概要

urllib3 is a user-friendly HTTP client library for Python. 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. We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited: 1. Setting the `Proxy-Authorization` header without using urllib3 s built-in proxy support. 2. Not disabling HTTP redirects. 3. Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin. Users are advised to update to either version 1.26.19 or version 2.2.2. Users unable to upgrade may use the `Proxy-Authorization` header with urllib3 s `ProxyManager`, disable HTTP redirects using `redirects=False` when sending requests, or not user the `Proxy-Authorization` header as mitigations.

CVSS v3 指标

安全公告

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