CVE-2026-76166
Modcluster-core: mod_cluster advertise listener: unauthenticated dos via crafted multicast datagram
No known exploitation. EPSS puts it in the 62nd percentile. Only a workaround so far.
What to do
No fixed build is published yet. The vendor describes a workaround.
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
1.0% chance of exploitation activity in the next 30 days, which ranks it in the 62nd percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
9 events over 1 day, from the signal feeds we watch.
- Workaround availableworkaround available, record updated, record updated
- Workaround availablepublished, weakness classified, att&ck mapped, record updated
Affected products
- Red Hat JBoss Enterprise Application Platform 7Operating Systems / linux-distro
- Red Hat JBoss Enterprise Application Platform 8Enterprise Software / itsm-monitoring
- Red Hat JBoss Enterprise Application Platform Expansion PackOperating Systems / linux-distro
- Red Hat JBoss Web Server 5Enterprise Software / itsm-monitoring
- Red Hat JBoss Web Server 6Operating Systems / linux-distro
- Red Hat JBoss Web Server 7Operating Systems / linux-distro
- Red Hat Single Sign-On 7Security Products / identity-access-mgmt
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Scored 4.3 by NVD.
How it is reached
- Attack Vector AdjacentRequires access to the local network (e.g. same Wi-Fi, Bluetooth)
- Attack Complexity LowNo special conditions — the attack can be reliably reproduced
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope UnchangedImpact is limited to the vulnerable component itself
Impact if exploited
- Confidentiality NoneNo confidentiality impact
- Integrity NoneNo integrity impact
- Availability LowReduced performance or intermittent disruption of service
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
Sources
References in the record
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