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Vulnerability · Published Aug 19, 2026 · Assigned by redhat

CVE-2026-76166Modcluster-core: mod_cluster advertise listener: unauthenticated dos via crafted multicast datagram

Medium 4.3

In plain English

A medium-severity null pointer dereference in Red Hat JBoss Enterprise Application Platform 7 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.7% (higher than 86% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)2.7%top 13.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat JBoss Web Server 7.0.3 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 10 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 10 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 10 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 8 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 8 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 8 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 9 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 9 see references
Red Hat Red Hat JBoss Web Server 7.0 on RHEL 9 see references
Red Hat Red Hat JBoss Enterprise Application Platform 7 see references
Red Hat Red Hat JBoss Enterprise Application Platform 8 see references
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack see references
Red Hat Red Hat JBoss Web Server 5 see references
Red Hat Red Hat JBoss Web Server 6 see references
Red Hat Red Hat Single Sign-On 7 see references

Weakness: CWE-476 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References