Update dependency urllib3 to v2 [SECURITY] by renovate[bot] · Pull Request #5497 · mitodl/micromasters

renovate · 2026-03-31T22:37:38Z

ℹ️ Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package	Change	Age	Confidence
urllib3 (changelog)	`==1.26.5` → `==2.7.0`

`Cookie` HTTP header isn't stripped on cross-origin redirects

CVE-2023-43804 / GHSA-v845-jxx5-vc9f / PYSEC-2023-192

More information

Details

urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.

Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the Cookie header, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

Using an affected version of urllib3 (patched in v1.26.17 and v2.0.6)
Using the Cookie header on requests, which is mostly typical for impersonating a browser.
Not disabling HTTP redirects
Either not using HTTPS or for the origin server to redirect to a malicious origin.

Remediation

Upgrading to at least urllib3 v1.26.17 or v2.0.6
Disabling HTTP redirects using redirects=False when sending requests.
Not using the Cookie header.

Severity

CVSS Score: 7.4 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2023-43804 / GHSA-v845-jxx5-vc9f / PYSEC-2023-192

More information

Details

urllib3 is a user-friendly HTTP client library for Python. urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly. This issue has been patched in urllib3 version 1.26.17 or 2.0.5.

Severity

CVSS Score: 8.1 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3's request body not stripped after redirect from 303 status changes request method to GET

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4 / PYSEC-2023-212

More information

Details

urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 303 "See Other" after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although the behavior of removing the request body is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers.

From RFC 9110 Section 9.3.1:

A client SHOULD NOT generate content in a GET request unless it is made directly to an origin server that has previously indicated, in or out of band, that such a request has a purpose and will be adequately supported.

Affected usages

Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable.

Both of the following conditions must be true to be affected by this vulnerability:

If you're using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON)
The origin service is compromised and starts redirecting using 303 to a malicious peer or the redirected-to service becomes compromised.

Remediation

You can remediate this vulnerability with any of the following steps:

Upgrade to a patched version of urllib3 (v1.26.18 or v2.0.7)
Disable redirects for services that you aren't expecting to respond with redirects with redirects=False.
Disable automatic redirects with redirects=False and handle 303 redirects manually by stripping the HTTP request body.

Severity

CVSS Score: 5.7 / 10 (Medium)
Vector String: CVSS:4.0/AV:A/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4 / PYSEC-2023-212

More information

Details

urllib3 is a user-friendly HTTP client library for Python. urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 301, 302, or 303 after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although this behavior is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers. Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable. Both of the following conditions must be true to be affected by this vulnerability: 1. Using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON) and 2. The origin service is compromised and starts redirecting using 301, 302, or 303 to a malicious peer or the redirected-to service becomes compromised. This issue has been addressed in versions 1.26.18 and 2.0.7 and users are advised to update to resolve this issue. Users unable to update should disable redirects for services that aren't expecting to respond with redirects with redirects=False and disable automatic redirects with redirects=False and handle 301, 302, and 303 redirects manually by stripping the HTTP request body.

Severity

CVSS Score: 4.2 / 10 (Medium)
Vector String: CVSS:3.1/AV:A/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

CVE-2024-37891 / GHSA-34jh-p97f-mpxf / PYSEC-2026-1995

More information

Details

When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.

However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.

Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.

Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
Not disabling HTTP redirects.
Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.

Remediation

Using the Proxy-Authorization header with urllib3's ProxyManager.
Disabling HTTP redirects using redirects=False when sending requests.
Not using the Proxy-Authorization header.

Severity

CVSS Score: 4.4 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

CVE-2024-37891 / GHSA-34jh-p97f-mpxf / PYSEC-2026-1995

More information

Details

When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.

However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.

Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.

Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
Not disabling HTTP redirects.
Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.

Remediation

Using the Proxy-Authorization header with urllib3's ProxyManager.
Disabling HTTP redirects using redirects=False when sending requests.
Not using the Proxy-Authorization header.

Severity

CVSS Score: 4.4 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation

CVE-2025-50181 / GHSA-pq67-6m6q-mj2v / PYSEC-2026-1999

More information

Details

urllib3 handles redirects and retries using the same mechanism, which is controlled by the Retry object. The most common way to disable redirects is at the request level, as follows:

resp = urllib3.request("GET", "https://httpbin.org/redirect/1", redirect=False)
print(resp.status)

##### 302

However, it is also possible to disable redirects, for all requests, by instantiating a PoolManager and specifying retries in a way that disable redirects:

import urllib3

http = urllib3.PoolManager(retries=0)  # should raise MaxRetryError on redirect
http = urllib3.PoolManager(retries=urllib3.Retry(redirect=0))  # equivalent to the above
http = urllib3.PoolManager(retries=False)  # should return the first response

resp = http.request("GET", "https://httpbin.org/redirect/1")

However, the retries parameter is currently ignored, which means all the above examples don't disable redirects.

Affected usages

Passing retries on PoolManager instantiation to disable redirects or restrict their number.

By default, requests and botocore users are not affected.

Impact

Redirects are often used to exploit SSRF vulnerabilities. An application attempting to mitigate SSRF or open redirect vulnerabilities by disabling redirects at the PoolManager level will remain vulnerable.

Remediation

You can remediate this vulnerability with the following steps:

Upgrade to a patched version of urllib3. If your organization would benefit from the continued support of urllib3 1.x, please contact sethmichaellarson@gmail.com to discuss sponsorship or contribution opportunities.
Disable redirects at the request() level instead of the PoolManager() level.

Severity

CVSS Score: 5.3 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation

CVE-2025-50181 / GHSA-pq67-6m6q-mj2v / PYSEC-2026-1999

More information

Details

urllib3 handles redirects and retries using the same mechanism, which is controlled by the Retry object. The most common way to disable redirects is at the request level, as follows:

resp = urllib3.request("GET", "https://httpbin.org/redirect/1", redirect=False)
print(resp.status)

##### 302

However, it is also possible to disable redirects, for all requests, by instantiating a PoolManager and specifying retries in a way that disable redirects:

import urllib3

http = urllib3.PoolManager(retries=0)  # should raise MaxRetryError on redirect
http = urllib3.PoolManager(retries=urllib3.Retry(redirect=0))  # equivalent to the above
http = urllib3.PoolManager(retries=False)  # should return the first response

resp = http.request("GET", "https://httpbin.org/redirect/1")

However, the retries parameter is currently ignored, which means all the above examples don't disable redirects.

Affected usages

Passing retries on PoolManager instantiation to disable redirects or restrict their number.

By default, requests and botocore users are not affected.

Impact

Redirects are often used to exploit SSRF vulnerabilities. An application attempting to mitigate SSRF or open redirect vulnerabilities by disabling redirects at the PoolManager level will remain vulnerable.

Remediation

You can remediate this vulnerability with the following steps:

Upgrade to a patched version of urllib3. If your organization would benefit from the continued support of urllib3 1.x, please contact sethmichaellarson@gmail.com to discuss sponsorship or contribution opportunities.
Disable redirects at the request() level instead of the PoolManager() level.

Severity

CVSS Score: 5.3 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3 streaming API improperly handles highly compressed data

CVE-2025-66471 / GHSA-2xpw-w6gg-jr37 / PYSEC-2026-1994

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation.

The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side, even if the application only requested a small chunk of data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier to stream large compressed responses or content from untrusted sources.

stream(), read(amt=256), read1(amt=256), read_chunked(amt=256), readinto(b) are examples of urllib3.HTTPResponse method calls using the affected logic unless decoding is disabled explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library avoids decompressing data that exceeds the requested amount.

If your environment contains a package facilitating the Brotli encoding, upgrade to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 too. These versions are enforced by the urllib3[brotli] extra in the patched versions of urllib3.

Credits

The issue was reported by @Cycloctane.
Supplemental information was provided by @stamparm during a security audit performed by 7ASecurity and facilitated by OSTIF.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

urllib3 allows an unbounded number of links in the decompression chain

CVE-2025-66418 / GHSA-gm62-xv2j-4w53 / PYSEC-2026-1998

More information

Details

Impact

urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, zstd).

However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier for HTTP requests to untrusted sources unless they disable content decoding explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library limits the number of links to 5.

If upgrading is not immediately possible, use preload_content=False and ensure that resp.headers["content-encoding"] contains a safe number of encodings before reading the response content.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

urllib3 streaming API improperly handles highly compressed data

CVE-2025-66471 / GHSA-2xpw-w6gg-jr37 / PYSEC-2026-1994

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation.

The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side, even if the application only requested a small chunk of data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier to stream large compressed responses or content from untrusted sources.

stream(), read(amt=256), read1(amt=256), read_chunked(amt=256), readinto(b) are examples of urllib3.HTTPResponse method calls using the affected logic unless decoding is disabled explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library avoids decompressing data that exceeds the requested amount.

If your environment contains a package facilitating the Brotli encoding, upgrade to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 too. These versions are enforced by the urllib3[brotli] extra in the patched versions of urllib3.

Credits

The issue was reported by @Cycloctane.
Supplemental information was provided by @stamparm during a security audit performed by 7ASecurity and facilitated by OSTIF.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3 allows an unbounded number of links in the decompression chain

CVE-2025-66418 / GHSA-gm62-xv2j-4w53 / PYSEC-2026-1998

More information

Details

Impact

urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, zstd).

However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier for HTTP requests to untrusted sources unless they disable content decoding explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library limits the number of links to 5.

If upgrading is not immediately possible, use preload_content=False and ensure that resp.headers["content-encoding"] contains a safe number of encodings before reading the response content.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

Decompression-bomb safeguards bypassed when following HTTP redirects (streaming API)

CVE-2026-21441 / GHSA-38jv-5279-wg99 / PYSEC-2026-1996

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption.

However, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client (high CPU usage and large memory allocations for decompressed data; CWE-409).

Affected usages

Applications and libraries using urllib3 version 2.6.2 and earlier to stream content from untrusted sources by setting preload_content=False when they do not disable redirects.

Remediation

Upgrade to at least urllib3 v2.6.3 in which the library does not decode content of redirect responses when preload_content=False.

If upgrading is not immediately possible, disable redirects by setting redirect=False for requests to untrusted source.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Decompression-bomb safeguards bypassed when following HTTP redirects (streaming API)

CVE-2026-21441 / GHSA-38jv-5279-wg99 / PYSEC-2026-1996

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption.

However, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client (high CPU usage and large memory allocations for decompressed data; CWE-409).

Affected usages

Applications and libraries using urllib3 version 2.6.2 and earlier to stream content from untrusted sources by setting preload_content=False when they do not disable redirects.

Remediation

Upgrade to at least urllib3 v2.6.3 in which the library does not decode content of redirect responses when preload_content=False.

If upgrading is not immediately possible, disable redirects by setting redirect=False for requests to untrusted source.

Severity

CVSS Score: 8.9 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3: Sensitive headers forwarded across origins in proxied low-level redirects

CVE-2026-44431 / GHSA-qccp-gfcp-xxvc / PYSEC-2026-141

More information

Details

Impact

When following cross-origin redirects for requests made using urllib3’s high-level APIs, such as urllib3.request(), PoolManager.request(), and ProxyManager.request(), sensitive headers — Authorization, Cookie, and Proxy-Authorization (defined in Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT) — are stripped by default, as expected.

However, cross-origin redirects followed from the low-level API via ProxyManager.connection_from_url().urlopen(..., assert_same_host=False) still forward these sensitive headers.

Affected usage

Applications and libraries using urllib3 versions earlier than 2.7.0 may be affected if they allow cross-origin redirects while making requests through HTTPConnection.urlopen() instances created via ProxyManager.connection_from_url().

Remediation

Upgrade to urllib3 version 2.7.0 or later, in which sensitive headers are stripped from redirects followed by HTTPConnection.

If upgrading is not immediately possible, avoid using this low-level redirect flow for cross-origin redirects. If appropriate for your use case, switch to ProxyManager.request().

Severity

CVSS Score: 8.2 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2026-44431 / GHSA-qccp-gfcp-xxvc / PYSEC-2026-141

More information

Details

urllib3 is an HTTP client library for Python. From 1.23 to before 2.7.0, cross-origin redirects followed from the low-level API via ProxyManager.connection_from_url().urlopen(..., assert_same_host=False) still forward these sensitive headers. This vulnerability is fixed in 2.7.0.

Severity

CVSS Score: 5.3 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References

https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

Release Notes

urllib3/urllib3 (urllib3)

`v2.7.0`

Compare Source

=======================

Security

Addressed high-severity security issues.
Impact was limited to specific use cases detailed in the accompanying
advisories; overall user exposure was estimated to be marginal.

Decompression-bomb safeguards of the streaming API were bypassed:
1. When HTTPResponse.drain_conn() was called after the response had been
  read and decompressed partially.
2. During the second HTTPResponse.read(amt=N) or
  HTTPResponse.stream(amt=N) call when the response was decompressed
  using the official Brotli <https://pypi.org/project/brotli/>__ library.
See GHSA-mf9v-mfxr-j63j <https://github.com/urllib3/urllib3/security/advisories/GHSA-mf9v-mfxr-j63j>__
for details.
HTTP pools created using ProxyManager.connection_from_url did not strip
sensitive headers specified in Retry.remove_headers_on_redirect when
redirecting to a different host.
(GHSA-qccp-gfcp-xxvc <https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc>__)

Deprecations and Removals

Used FutureWarning instead of DeprecationWarning for better
visibility of existing deprecation notices. Rescheduled the removal of
deprecated features to version 3.0.
(#3763 <https://github.com/urllib3/urllib3/issues/3763>__)
Removed support for end-of-life Python 3.9.
(#3720 <https://github.com/urllib3/urllib3/issues/3720>__)
Removed support for end-of-life PyPy3.10.
(#4979 <https://github.com/urllib3/urllib3/issues/4979>__)
Bumped the minimum supported pyOpenSSL version to 19.0.0.
(#3777 <https://github.com/urllib3/urllib3/issues/3777>__)

Bugfixes

Fixed a bug where HTTPResponse.read(amt=None) was ignoring decompressed
data buffered from previous partial reads.
(#3636 <https://github.com/urllib3/urllib3/issues/3636>__)
Fixed a bug where HTTPResponse.read() could cache only part of the
response after a partial read when cache_content=True.
(#4967 <https://github.com/urllib3/urllib3/issues/4967>__)
Fixed HTTPResponse.stream() and HTTPResponse.read_chunked() to handle
amt=0.
(#3793 <https://github.com/urllib3/urllib3/issues/3793>__)
Updated _TYPE_BODY type alias to include missing Iterable[str],
matching the documented and runtime behavior of chunked request bodies.
(#3798 <https://github.com/urllib3/urllib3/issues/3798>__)
Fixed LocationParseError when paths resembling schemeless URIs were
passed to HTTPConnectionPool.urlopen().
(#3352 <https://github.com/urllib3/urllib3/issues/3352>__)
Fixed BaseHTTPResponse.readinto() type annotation to accept
memoryview in addition to bytearray, matching the
io.RawIOBase.readinto contract and enabling use with
io.BufferedReader without type errors.
(#3764 <https://github.com/urllib3/urllib3/issues/3764>__)

`v2.6.3`

Compare Source

==================

Fixed a high-severity security issue where decompression-bomb safeguards of
the streaming API were bypassed when HTTP redirects were followed.
(GHSA-38jv-5279-wg99 <https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99>__)
Started treating Retry-After times greater than 6 hours as 6 hours by
default. (#3743 <https://github.com/urllib3/urllib3/issues/3743>__)
Fixed urllib3.connection.VerifiedHTTPSConnection on Emscripten.
(#3752 <https://github.com/urllib3/urllib3/issues/3752>__)

`v2.6.2`

Compare Source

==================

Fixed HTTPResponse.read_chunked() to properly handle leftover data in
the decoder's buffer when reading compressed chunked responses.
(#3734 <https://github.com/urllib3/urllib3/issues/3734>__)

`v2.6.1`

Compare Source

==================

Restore previously removed HTTPResponse.getheaders() and
HTTPResponse.getheader() methods.
(#3731 <https://github.com/urllib3/urllib3/issues/3731>__)

`v2.6.0`

Compare Source

==================

Security

Fixed a security issue where streaming API could improperly handle highly
compressed HTTP content ("decompression bombs") leading to excessive resource
consumption even when a small amount of data was requested. Reading small
chunks of compressed data is safer and much more efficient now.
(GHSA-2xpw-w6gg-jr37 <https://github.com/urllib3/urllib3/security/advisories/GHSA-2xpw-w6gg-jr37>__)
Fixed a security issue where an attacker could compose an HTTP response with
virtually unlimited links in the Content-Encoding header, potentially
leading to a denial of service (DoS) attack by exhausting system resources
during decoding. The number of allowed chained encodings is now limited to 5.
(GHSA-gm62-xv2j-4w53 <https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53>__)

.. caution::

If urllib3 is not installed with the optional urllib3[brotli] extra, but
your environment contains a Brotli/brotlicffi/brotlipy package anyway, make
sure to upgrade it to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 to
benefit from the security fixes and avoid warnings. Prefer using
urllib3[brotli] to install a compatible Brotli package automatically.
If you use custom decompressors, please make sure to update them to
respect the changed API of urllib3.response.ContentDecoder.

Features

Enabled retrieval, deletion, and membership testing in HTTPHeaderDict using bytes keys. (#3653 <https://github.com/urllib3/urllib3/issues/3653>__)
Added host and port information to string representations of HTTPConnection. (#3666 <https://github.com/urllib3/urllib3/issues/3666>__)
Added support for Python 3.14 free-threading builds explicitly. (#3696 <https://github.com/urllib3/urllib3/issues/3696>__)

Removals

Removed the HTTPResponse.getheaders() method in favor of HTTPResponse.headers.
Removed the HTTPResponse.getheader(name, default) method in favor of HTTPResponse.headers.get(name, default). (#3622 <https://github.com/urllib3/urllib3/issues/3622>__)

Bugfixes

Fixed redirect handling in urllib3.PoolManager when an integer is passed
for the retries parameter. (#3649 <https://github.com/urllib3/urllib3/issues/3649>__)
Fixed HTTPConnectionPool when used in Emscripten with no explicit port. (#3664 <https://github.com/urllib3/urllib3/issues/3664>__)
Fixed handling of SSLKEYLOGFILE with expandable variables. (#3700 <https://github.com/urllib3/urllib3/issues/3700>__)

Misc

Changed the zstd extra to install backports.zstd instead of zstandard on Python 3.13 and before. (#3693 <https://github.com/urllib3/urllib3/issues/3693>__)
Improved the performance of content decoding by optimizing BytesQueueBuffer cla

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renovate · 2026-03-31T22:37:40Z

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File name: uv.lock

Command failed: uv lock --upgrade-package urllib3
Using CPython 3.11.16
  × No solution found when resolving dependencies for split (markers:
  │ python_full_version >= '3.12'):
  ╰─▶ Because opensearch-py<=1.0.0 depends on urllib3>=1.21.1,<2 and your
      project depends on opensearch-py==1.0.0, we can conclude that your
      project depends on urllib3>=1.21.1,<2.
      And because your project depends on urllib3==2.7.0, we can conclude that
      your project's requirements are unsatisfiable.

hint: While the active Python version is 3.11, the resolution failed for other Python versions supported by your project. Consider limiting your project's supported Python versions using `requires-python`.

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Update dependency urllib3 to v2 [SECURITY]

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Update dependency urllib3 to v2 [SECURITY] - #5497

Update dependency urllib3 to v2 [SECURITY]#5497
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renovate Bot commented Mar 31, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Cookie HTTP header isn't stripped on cross-origin redirects

Details

Affected usages

Remediation

Severity

References

CVE-2023-43804 / GHSA-v845-jxx5-vc9f / PYSEC-2023-192

Details

Severity

References

urllib3's request body not stripped after redirect from 303 status changes request method to GET

Details

Affected usages

Remediation

Severity

References

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4 / PYSEC-2023-212

Details

Severity

References

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

Details

Affected usages

Remediation

Severity

References

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

Details

Affected usages

Remediation

Severity

References

urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation

Details

Affected usages

Impact

Remediation

Severity

References

urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation

Details

Affected usages

Impact

Remediation

Severity

References

urllib3 streaming API improperly handles highly compressed data

Details

Impact

Affected usages

Remediation

Credits

Severity

References

urllib3 allows an unbounded number of links in the decompression chain

Details

Impact

Affected usages

Remediation

Severity

References

urllib3 streaming API improperly handles highly compressed data

Details

Impact

Affected usages

Remediation

Credits

Severity

References

urllib3 allows an unbounded number of links in the decompression chain

Details

Impact

Affected usages

Remediation

Severity

References

renovate Bot commented Mar 31, 2026 •

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`Cookie` HTTP header isn't stripped on cross-origin redirects

`v2.7.0`

`v2.6.3`

`v2.6.2`

`v2.6.1`

`v2.6.0`

renovate Bot commented Mar 31, 2026 •

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