CVE-2026-76166 Modcluster-core: mod_cluster advertise listener: unauthenticated dos via crafted multicast datagram
An unauthenticated attacker can cause a permanent denial of service in the mod_cluster advertise listener by sending a crafted UDP multicast datagram.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-76166?
CVE-2026-76166 is a medium-severity vulnerability in Red Hat JBoss Enterprise Application Platform 7, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-476
Which versions are affected by CVE-2026-76166?
How do I fix CVE-2026-76166?
No fix has been published for CVE-2026-76166 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-76166 being exploited?
There is no known exploitation of CVE-2026-76166 in the wild and no public exploit code.
Sources
Also known as GHSA-p4rg-ffff-6pmm.