CVE-2021-28363EPSS p81.9%

CVE-2021-28363CVE-2021-28363

python / urllib3

Description

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.

Scoring

CVSS 6.5 ()
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS2.17% probability of exploitation · percentile 81.9% · 2026-10-17T12:00:28Z
Last modified2026-10-14
Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.