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CVE-2026-27459

pyOpenSSL DTLS cookie callback buffer overflow

Published: Mar 17, 2026Updated: Jul 30, 2026 Sources: CVE List NVD GHSACWE-120
9.8CRITICAL
NVD MITRE
EPSS Score
0.7%
Top 50.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-120

Affected Products

pyca
oss-project·GBaka py ca, pyca/cryptography
pyopensslLibrary
OSS Libraries / pypi
PyPI
package-ecosystem
pyopenssl
OSS Libraries
pyopenssl
oss-project
pyopensslLibrary
OSS Libraries / generic-library

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
Privilege Escalation
View detailed technique mapping

References

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
github.com
and 23 more references View all →

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