CVE-2026-56820

Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks

CRITICAL 9.1EPSS 0.3%

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, `OcspClient` does not validate that the `CertificateID` in an OCSP response matches the requested `CertificateID`, which can lead to replay attack. `OcspClient.validateResponse` accepts a legitimately signed `GOOD` status response for an unrelated certificate issued by the same CA, allowing bypass of revocation checks for another certificate. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected: netty
CVSS v3.1 NVD: 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS v3.1 GITHUB: 7.4 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS: 0.31% chance of exploitation in the next 30 days, 23rd percentile
Published: 2026-07-21
Updated: 2026-07-24

Proof-of-concept exploits (1)

advisories/GHSA-272m-gcwp-mpwg

CVE-2026-56820

Proof-of-concept exploits (1)

Security advisories

References