CVE-2026-27459

Publication date 18 March 2026

Last updated 30 June 2026

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
pyopenssl	25.10 questing	Fixed 25.0.0-1ubuntu0.1
	24.04 LTS noble	Fixed 23.2.0-1ubuntu0.1
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

mdeslaur

only affects 22.0.0+

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
pyopenssl	Upstream: https://github.com/pyca/pyopenssl/pull/1479 Upstream: 57f09bb

Severity score breakdown

CVSS version:

Base score 7.2 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	High
Attack requirements	Present
Privileges required	None
User interaction	None
Vulnerable system - Confidentiality impact	High
Vulnerable system - Integrity impact	High
Vulnerable system - Availability impact	High
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	7.2 · High
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Base score 8.1 · High