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.
Affected products
pyopenssl: pyopenssl
References10
- github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8j… Vendor Advisory
- github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525… Patch
- github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a27011624… Release Notes
- access.redhat.com/errata/RHSA-2026:10754
- access.redhat.com/errata/RHSA-2026:11856
- access.redhat.com/errata/RHSA-2026:11916
- access.redhat.com/errata/RHSA-2026:11996
- access.redhat.com/errata/RHSA-2026:13508
- access.redhat.com/errata/RHSA-2026:13512
- access.redhat.com/errata/RHSA-2026:13545
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 4.0
-
7.2
HIGH
Score source: CNA
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 57 · as of 12 November 2026
- CWE
- CWE-120
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.