Improper Certificate Validation in Netty - CVE-2026-56820

Vulnerability identifier: #VU137574

CSH Severity: Medium

CVSS v4: 9.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-56820

CWE-ID: CWE-295

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to bypass certificate revocation checks.

The vulnerability exists due to improper certificate validation in OcspClient validateResponse when processing OCSP responses. A remote attacker can supply a legitimately signed OCSP response for an unrelated certificate to bypass certificate revocation checks.

Exploitation requires access to another valid, non-revoked certificate issued by the same certificate authority as the target certificate.

Netty
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
Development Tools Module
SUSE Package Hub 15
netty-tcnative-debugsource
netty-tcnative
netty
netty-javadoc

Install security update from vendor's website.

Netty - addressed in versions 4.1.136, 4.2.16
netty-tcnative-debugsource - update to 2.0.80-150200.3.48.1
netty-tcnative - update to 2.0.80-150200.3.48.1
netty - update to 4.1.136-150200.4.53.1
netty-javadoc - update to 4.1.136-150200.4.53.1

• https://github.com/netty/netty/security/advisories/GHSA-272m-gcwp-mpwg

• Multiple vulnerabilities in Netty
• SUSE update for netty, netty-tcnative