pyOpenSSL DTLS cookie callback buffer overflow (pyca pyopenssl)

CVE-2026-27459

HIGH 7.2

At a glance

Source: NVD
EPSS: EPSS 0.73 % · percentile 54 (2026-10-29)
State: PUBLISHED
Published: 2026-03-17 23:34 UTC
Updated: 2026-09-11 12:09 UTC
Assigner: GitHub_M
NVD status: Modified

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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.

Weaknesses (CWE)

CWE-120 — Buffer Copy without Checking Size of Input

References

Scores

Version	Score	Vector	Scored by
CVSS 4.0	HIGH 7.2	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	GitHub_M
CVSS 3.1	HIGH 8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	redhat-SADP
CVSS 4.0	HIGH 7.2	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	NVD · security-advisories@github.com (Secondary)
CVSS 3.1	CRITICAL 9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	NVD · nvd@nist.gov (Primary)
CVSS 3.1	HIGH 8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary)

Advisories

GHSA-5pwr-322w-8jr4 — pyOpenSSL DTLS cookie callback buffer overflow
PYSEC-2026-2269 — 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_gen

European references

ENISA EUVD · EUVD-2026-12677
GCVE · GCVE-0-2026-27459

CERT-FR advisories

CERTFR-2026-AVI-0901 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
CERTFR-2026-AVI-0736 — Multiples vulnérabilités dans les produits Splunk · cert.ssi.gouv.fr
CERTFR-2026-AVI-0667 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
CERTFR-2026-AVI-0550 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
CERTFR-2026-AVI-0341 — Multiples vulnérabilités dans les produits Microsoft · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

cpe:2.3:a:pyopenssl:pyopenssl:*:*:*:*:*:*:*:* ≥ 22.0.0 < 26.0.0

Affected products

Product	Versions
pyca · pyopenssl	affected >= 22.0.0, < 26.0.0

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)	Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD

⚠️ pyOpenSSL DTLS cookie callback buffer overflow (pyca pyopenssl)