High 7.2Published Mar 17, 2026

CVE-2026-27459pyOpenSSL DTLS cookie callback buffer overflow

Updated under an hour ago (Oct 26, 2026, 11:00 PM ET)

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It affects pyca pyopenssl and 17 other products. Add what you run to find out whether that includes you.

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Every CVE for pyca pyopenssl

Exploited in the last 30 days

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.

CVSS: 7.2 HIGH (v4.0, CNA)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
Weakness (CWE): CWE-120
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Modified
Record last updated: Sep 11, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pyca pyopenssl pyca:pyopenssl (from the name)	from 22.0.0, < 26.0.0	CNA record
Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 8 redhat:ansible_automation_platform	from 0:26.0.0-1.el8ap not affected	CISA ADP
Red Hat Red Hat Satellite 6.16 for RHEL 8 redhat:satellite	from 0:24.1.0-2.el8pc not affected	CISA ADP
Red Hat Red Hat Satellite 6.16 for RHEL 8 redhat:satellite_capsule	from 0:24.1.0-2.el8pc not affected	CISA ADP
Red Hat RHUI 4 for RHEL 8 redhat:rhui	from 0:24.1.0-2.el8ui not affected	CISA ADP
Red Hat Red Hat Hardened Images redhat:hummingbird	from 2.20.0-0.8.hum1 not affected	CISA ADP
Red Hat Red Hat Quay 3.10 redhat:quay	from 1776736910 not affected	CISA ADP
Red Hat Red Hat Trusted Artifact Signer 1.4 redhat:trusted_artifact_signer	from 1775815407 not affected	CISA ADP
Red Hat Confidential Compute Attestation redhat:confidential_compute_attestation	1	CISA ADP
Red Hat Exploit Intelligence redhat:exploit_intelligence	0	CISA ADP
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References

References

https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4	x-refsource-confirm, vendor-advisory
https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408	x-refsource-misc, patch
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst	x-refsource-misc, release-notes
https://access.redhat.com/errata/RHSA-2026:10754
https://access.redhat.com/errata/RHSA-2026:11856
https://access.redhat.com/errata/RHSA-2026:11916
https://access.redhat.com/errata/RHSA-2026:11996
https://access.redhat.com/errata/RHSA-2026:13508
https://access.redhat.com/errata/RHSA-2026:13512
https://access.redhat.com/errata/RHSA-2026:13545
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.