CVE-2026-27459 — Vulnerability in pyopenssl — CVE Details
CRITICAL
Published March 18, 2026Updated July 13, 2026Source: osv
Summary
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.
Advisory Timeline
- First published March 18, 2026 (208 days ago).
- Last revised July 13, 2026 — 117 days after initial publication.
Remediation
Upgrade to the fixed version using your package manager.
pip
Update pyopenssl to 26.0.0 or laterpip install "pyopenssl>=26.0.0"
After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.
Affected Packages (1)
Affects 1 ecosystem: pypi (1).
| Package | Ecosystem | Affected | Fixed In |
|---|---|---|---|
| pyopenssl | pypi | 22.0.0, 22.1.0, 23.0.0, 23.1.0 (+11 more) | 26.0.0 |
CVSS Score Breakdown
What the CVSS (Common Vulnerability Scoring System) 9.8 score means for each attack dimension.
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://access.redhat.com/security/cve/CVE-2026-27459WEB
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27459.jsonWEB
- https://access.redhat.com/errata/RHSA-2026:10754ADVISORY
- https://access.redhat.com/errata/RHSA-2026:11856ADVISORY
- https://access.redhat.com/errata/RHSA-2026:11916ADVISORY
- https://access.redhat.com/errata/RHSA-2026:11996ADVISORY
- https://access.redhat.com/errata/RHSA-2026:13508ADVISORY
- https://access.redhat.com/errata/RHSA-2026:13512ADVISORY
- https://access.redhat.com/errata/RHSA-2026:13545ADVISORY
- https://access.redhat.com/errata/RHSA-2026:13553ADVISORY
- https://access.redhat.com/errata/RHSA-2026:14835ADVISORY
- https://access.redhat.com/errata/RHSA-2026:14873ADVISORY
- https://access.redhat.com/errata/RHSA-2026:14874ADVISORY
- https://access.redhat.com/errata/RHSA-2026:19375ADVISORY
- https://access.redhat.com/errata/RHSA-2026:21017ADVISORY
- https://access.redhat.com/errata/RHSA-2026:22465ADVISORY
- https://access.redhat.com/errata/RHSA-2026:24853ADVISORY
- https://access.redhat.com/errata/RHSA-2026:7224ADVISORY
- https://access.redhat.com/errata/RHSA-2026:8437ADVISORY
- https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rstADVISORY
- https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4ADVISORY
- https://bugzilla.redhat.com/show_bug.cgi?id=2448503REPORT
- https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408FIX
Frequently Asked Questions
- What is CVE-2026-27459?
- This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.8/10).
- How do I check if my project is affected by CVE-2026-27459?
- CVE-2026-27459 affects pyopenssl. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-27459 and 200,000+ other known vulnerabilities.
Severity & Exploitability
CVSS Score
9.8
Exploitation is straightforward and causes maximum impact. Patch immediately.
Also Known As
PYSEC-2026-2269
GHSA-5pwr-322w-8jr4
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