CVE-2026-27459

EUVD-2026-12677
pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to `set_cookie_generate_callback` returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.
Classic Buffer Overflow
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
9.8 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 7.2%
Affected Products (NVD)
VendorProductVersion
pyopensslpyopenssl
22.0.0 ≤
𝑥
< 26.0.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
pyopenssl
bookworm
no-dsa
bullseye
20.0.1-1
fixed
forky
26.1.0-1
fixed
sid
26.1.0-1
fixed
trixie
no-dsa
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
pyopenssl
bionic
not-affected
focal
not-affected
jammy
not-affected
noble
Fixed 23.2.0-1ubuntu0.1
released
questing
Fixed 25.0.0-1ubuntu0.1
released
trusty
not-affected
xenial
not-affected
Common Weakness Enumeration
Vulnerability Media Exposure
References
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst
https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408
https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4