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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-76166
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-19 10:16:38 UTC
Updated2026-08-19 10:16:38 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

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

Problem Types: CWE-476 | CWE-476 NULL Pointer Dereference

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary4.3MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
3.1CNACVSS4.3MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat JBoss Enterprise Application Platform 7 Not specified Not specified
CNA Red Hat Red Hat JBoss Enterprise Application Platform 8 Not specified Not specified
CNA Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack Not specified Not specified
CNA Red Hat Red Hat JBoss Web Server 5 Not specified Not specified
CNA Red Hat Red Hat JBoss Web Server 6 Not specified Not specified
CNA Red Hat Red Hat JBoss Web Server 7 Not specified Not specified
CNA Red Hat Red Hat Single Sign-On 7 Not specified Not specified

References

ReferenceSourceLinkTags
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
access.redhat.com/security/cve/CVE-2026-76166 [email protected] access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Red Hat would like to thank Kien Pham (Ninh Thanh Cyber Security (NTCS)) and Ta Duc Thien (Ninh Thanh Cyber Security (NTCS)) for reporting this issue. (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-07-23T00:00:00.000ZReported to Red Hat.
CNA2026-08-04T00:00:00.000ZMade public.

Workarounds

CNA: Disable multicast-based proxy advertisement and use static proxy configuration instead. When advertisement must be enabled, ensure the multicast network segment (default 224.0.1.105:23364) is properly isolated and not accessible from untrusted network segments.

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