Time-of-check Time-of-use (TOCTOU) Race Condition in Netty - CVE-2026-56822

Vulnerability identifier: #VU137573

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-2026-56822

CWE-ID: CWE-367

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to a time-of-check time-of-use race condition in OcspServerCertificateValidator when forwarding the TLS handshake completion event before asynchronous OCSP validation completes. A remote attacker can present a revoked server certificate and complete a TLS handshake to disclose sensitive information.

Client applications may send application data or process incoming application data during the interval before the OCSP check closes the channel.

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-wc96-39fc-566f

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