critical9.8
CVE-2026-27459
pyOpenSSL DTLS cookie callback buffer overflow
Impact
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. Cookie values that are too long are now rejected.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | pyopenssl | >= 22.0.0, < 26.0.0 | 26.0.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Pyopenssl | Pyopenssl | from 22.0.0 before 26.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst
- https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408
- https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4
- 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