The urllib3 library 1.26.x before 1.26.4 for Python omits SSL certificate validation in some cases involving HTTPS to HTTPS proxies. The initial connection to the HTTPS proxy (if an SSLContext isn't given via proxy_config) doesn't verify th…

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

The urllib3 library 1.26.x before 1.26.4 for Python omits SSL certificate validation in some cases involving HTTPS to HTTPS proxies. The initial connection to the HTTPS proxy (if an SSLContext isn't given via proxy_config) doesn't verify the hostname of the certificate. This means certificates for different servers that still validate properly with the default urllib3 SSLContext will be silently accepted.

Source published

15 Mar 2021 00:00:00 UTC

Source modified

14 Oct 2026 11:39:31 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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