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CVE-2026-76166

MEDIUM 4.3

Published 2026-08-19 · Last modified 2026-08-20

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.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.8%chance of exploitation in 30 days · 55th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

4.3CVSS 3.1 · MEDIUM

  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityLow

What an attacker needs

  • ⚠Access: Must sit on the same / adjacent network
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-76166/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-76166/poc.json

Affected

Vendors 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

Weakness (CWE)

  • CWE-476: NULL Pointer Dereference

CVSS vector

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

All CVSS metrics

  • MEDIUM 4.3 v3.1 · CNA Primary
    CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
  • MEDIUM 4.3 v3.1 · NVD Secondary
    CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

Technical & other

Sources: NVD · CVE.org · EPSS