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Vulnerability record · CVE-2026-27459 · published 18 March 2026

CVE-2026-27459: Pyopenssl classic buffer overflow vulnerability

Pyopenssl · Pyopenssl

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.

7.2 CVSS 4.0 High EPSS 0.88% · top 42.5% CWE-120 · Classic buffer overflow
7.2CVSS 4.0 base score
0.88%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
26References
10 Sep 2026Last modified by NVD

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.

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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst Release Notes
https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408 Patch
https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4 Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:10754
https://access.redhat.com/errata/RHSA-2026:11856
https://access.redhat.com/errata/RHSA-2026:11916
https://access.redhat.com/errata/RHSA-2026:11996
https://access.redhat.com/errata/RHSA-2026:13508
https://access.redhat.com/errata/RHSA-2026:13512
https://access.redhat.com/errata/RHSA-2026:13545
https://access.redhat.com/errata/RHSA-2026:13553
https://access.redhat.com/errata/RHSA-2026:14835
https://access.redhat.com/errata/RHSA-2026:14873
https://access.redhat.com/errata/RHSA-2026:14874
https://access.redhat.com/errata/RHSA-2026:19375
https://access.redhat.com/errata/RHSA-2026:21017
https://access.redhat.com/errata/RHSA-2026:22465
https://access.redhat.com/errata/RHSA-2026:24853
https://access.redhat.com/errata/RHSA-2026:48085
https://access.redhat.com/errata/RHSA-2026:48758
https://access.redhat.com/errata/RHSA-2026:59153
https://access.redhat.com/errata/RHSA-2026:7224
https://access.redhat.com/errata/RHSA-2026:8437
https://access.redhat.com/security/cve/CVE-2026-27459
https://bugzilla.redhat.com/show_bug.cgi?id=2448503
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27459.json

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Source: NIST National Vulnerability Database (record CVE-2026-27459), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.