CVE-2026-27459 PUBLISHED

pyOpenSSL DTLS cookie callback buffer overflow

Assigner: GitHub_M
Reserved: 19.02.2026 Published: 17.03.2026 Updated: 17.03.2026

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.

Metrics

CVSS 4.0

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
CVSS Score: 7.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	High	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	High	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	pyca
Product	pyopenssl
Versions	Version >= 22.0.0, < 26.0.0 is affected

References

Problem Types

CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') CWE