What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-19 · updated 2026-08-20
• Weakness: CWE-476

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

• Red Hat JBoss Enterprise Application Platform 7: all versions
• Red Hat JBoss Enterprise Application Platform 8: all versions
• Red Hat JBoss Enterprise Application Platform Expansion Pack: all versions
• Red Hat JBoss Web Server 6: all versions
• Red Hat JBoss Web Server 7: all versions
• Red Hat Single Sign-On 7: all versions

References

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

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