Medium [CVE-2026-76166] mod_cluster Advertise Listener: unauthenticated DoS via crafted multicast datagram
This medium-severity Red Hat Linux advisory covers CVE-2026-76166 affecting Red Hat JBoss Enterprise Application Platform 7, Red Hat JBoss Enterprise Application Platform 8, Red Hat JBoss Enterprise Application Platform Expansion Pack.
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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. Red Hat severity: Moderate — CVSS 4.3 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Weakness: CWE-476. Affected Red Hat products: Red Hat JBoss Enterprise Application Platform 7; Red Hat JBoss Enterprise Application Platform 8; Red Hat JBoss Enterprise Application Platform Expansion Pack; Red Hat JBoss Web Server 5; Red Hat JBoss Web Server 6; Red Hat JBoss Web Server 7; Red Hat Single Sign-On 7.
Will not fix / out of support: Red Hat JBoss Web Server 5. Red Hat does not currently list a fixing RHSA for this CVE.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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