CVE-2026-27459
pyOpenSSL DTLS cookie callback buffer overflow
CVSS Score
8.1
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-120 |
| Vendor | pyca |
| Product | pyopenssl |
| Published | Mar 17, 2026 |
| Last Updated | Jul 20, 2026 |
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Affected Versions
pyca / pyopenssl
>= 22.0.0, < 26.0.0
References
github.com: https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4 github.com: https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408 github.com: https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-27459 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2448503 security.access.redhat.com: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27459.json access.redhat.com: https://access.redhat.com/errata/RHSA-2026:13512 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:10754 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:14874 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:13508 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:14873 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:14835 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:13553 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:13545 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:7224 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:11856 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:21017 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:24853 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:19375 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:22465 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:11916 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:11996 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:8437