🛡️ CVE-2026-27459 — pyopenssl

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-120 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-27459 is classified as CWE-120: Classic Buffer Overflow. Input is copied into a fixed-size buffer without a length check, overwriting memory past the end of it.

Affected software

CVE-2026-27459 is recorded against 1 package.

  • pyopenssl (from 22.0.0 up to 26.0.0)

Timeline and source

Published on 16 March 2026 and last revised on 30 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
github.com (Web)

CVE-2026-27459 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS 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
CWE CWE-120
Public Exploit ✅ No
Source OSV
Published 2026-03-16
Updated 2026-08-12
Modified 2026-07-30

Affected Packages

Software From version Fixed in
pyopenssl 22.0.0 26.0.0

Similar Threats

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