pyOpenSSL DTLS cookie callback buffer overflow
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 software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pyopenssl | >= 22.0.0, < 26.0.0 | 26.0.0 |
References
- https://access.redhat.com/security/cve/CVE-2026-27459
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27459.json
- 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-2026:7224
- https://access.redhat.com/errata/RHSA-2026:8437
- https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst
- https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4
- https://bugzilla.redhat.com/show_bug.cgi?id=2448503
- https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408
- https://nvd.nist.gov/vuln/detail/CVE-2026-27459
- https://github.com/pyca/pyopenssl
- 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- Weakness (CWE)
CWE-120- Platform
- Python (PyPI)
- Package
pyopenssl- Disclosed
- 16.03.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2269 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5pwr-322w-8jr4 - CC BY 4.0
Vulnerability history: pyopenssl
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 09.2013 03.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Low 1
Disclosures per year
- 2017: 0
- 2018: 2
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 2
earlier: 1
-
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