OpenSSL CVE-2026-27459
HIGH
GHSA-5pwr-322w-8jr4
CVSS VectorNVD
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:X/V:X/RE:X/U:X
Lifecycle Timeline
3Blast Radius
ecosystem impact- 219 pypi packages depend on pyopenssl (80 direct, 141 indirect)
Ecosystem-wide dependent count for version 22.0.0.
DescriptionNVD
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.
AnalysisAI
Buffer overflow in pyOpenSSL's cookie generation callback allows attackers to corrupt memory and potentially achieve remote code execution by supplying oversized cookie values exceeding 256 bytes. The vulnerability affects applications using custom cookie callbacks with OpenSSL integration, where insufficient length validation permits writing beyond allocated buffer boundaries. …
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RemediationAI
Within 24 hours: Identify all systems and applications using pyOpenSSL and document their versions. Within 7 days: Apply the available patch to all affected systems and test in non-production environments first. …
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External POC / Exploit Code
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