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CVE-2023-43804 Moderate

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

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.

Exploit probability 1.2%
Published October 4, 2023
Required by Not available
Last source change August 12, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

46 explicit affected versions

PyPI urllib3

85 explicit affected versions

PyPI urllib3

85 explicit affected versions

03 / CONNECTIONS

Connected vulnerabilities

04 / EVIDENCE

Source records

Open Source Vulnerabilities CVE-2023-43804

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.

View original source
Open Source Vulnerabilities GHSA-v845-jxx5-vc9f

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.

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Open Source Vulnerabilities PYSEC-2023-192

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.

View original source

05 / REFERENCES

Further evidence