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CVE-2026-76166

MEDIUMCVSS 4.3/10EPSS 0.84%

Last modified

CVE-2026-76166 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.84% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
4.3/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability
0.84%

55.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
Red HatRed Hat JBoss Enterprise Application Platform 7All versions
Red HatRed Hat JBoss Enterprise Application Platform 8All versions
Red HatRed Hat JBoss Enterprise Application Platform Expansion PackAll versions
Red HatRed Hat JBoss Web Server 5All versions
Red HatRed Hat JBoss Web Server 6All versions
Red HatRed Hat JBoss Web Server 7All versions
Red HatRed Hat Single Sign-On 7All versions

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-76166?
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.
How severe is CVE-2026-76166?
CVE-2026-76166 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.84% probability of exploitation in the next 30 days.
How do I fix CVE-2026-76166?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST