CVE-2026-76166

Summary

A flaw was found in mod_cluster's AdvertiseListenerImpl (org.jboss.modcluster core module). A single crafted UDP multicast datagram with a valid HTTP status line and a "Server:" header but without the "Date:", "Digest:", and "Sequence:" headers triggers a NullPointerException in verifyDigest() that is not caught by the worker thread's exception handler. This causes the advertise listener thread to terminate permanently. The failure is silent (isListening() continues to return true) and persists until the node is restarted. The crash occurs before the AdvertiseSecurityKey comparison, so deployments with a configured security key are still affected.

Affected Software

Weaknesses

• CWE-476: NULL Pointer Dereference

Workarounds

Disable multicast-based proxy advertisement and use static proxy configuration instead. When advertisement must be enabled, ensure the multicast network segment (default 224.0.1.105:23364) is properly isolated and not accessible from untrusted network segments.

References

• https://access.redhat.com/security/cve/CVE-2026-76166
• https://bugzilla.redhat.com/show_bug.cgi?id=2510883

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