CVE-2026-76166
Modcluster-core: mod_cluster advertise listener: unauthenticated dos via crafted multicast datagram
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.
Fixes and workarounds
Workaround
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.
Source: CNA: redhatAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| Red Hat JBoss Web Server 7.0.3 Red Hat mod_cluster-core
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 10 Red Hat jws7-mod_cluster
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:2.1.1-1.Final_redhat_00001.1.el10jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 10 Red Hat jws7-tomcat
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:11.0.21-10.redhat_00010.1.el10jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 10 Red Hat jws7-tomcat-native
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:1.3.7-4.redhat_4.el10jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 8 Red Hat jws7-mod_cluster
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:2.1.1-1.Final_redhat_00001.1.el8jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 8 Red Hat jws7-tomcat
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:11.0.21-10.redhat_00010.1.el8jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 8 Red Hat jws7-tomcat-native
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:1.3.7-4.redhat_4.el8jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 9 Red Hat jws7-mod_cluster
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:2.1.1-1.Final_redhat_00001.1.el9jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 9 Red Hat jws7-tomcat
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:11.0.21-10.redhat_00010.1.el9jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 7.0 on RHEL 9 Red Hat jws7-tomcat-native
https://access.redhat.com/downloads/content/package-browser/ |
≥ 0:1.3.7-4.redhat_4.el9jws; < * (unaffected, rpm)
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Enterprise Application Platform 7 Red Hat mod_cluster-core
https://access.redhat.com/jbossnetwork/restricted/listSoftware.html |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Enterprise Application Platform 8 Red Hat mod_cluster-core
https://access.redhat.com/jbossnetwork/restricted/listSoftware.html |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Enterprise Application Platform Expansion Pack Red Hat mod_cluster-core
https://access.redhat.com/jbossnetwork/restricted/listSoftware.html |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat JBoss Web Server 5 Red Hat mod_cluster-core
https://access.redhat.com/jbossnetwork/restricted/listSoftware.html |
Range not reported
Other versions: unknown |
CNA: redhat |
| Red Hat JBoss Web Server 6 Red Hat mod_cluster-core
https://access.redhat.com/jbossnetwork/restricted/listSoftware.html |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Single Sign-On 7 Red Hat mod_cluster-core
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 4.3 medium |
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | CNA: redhat |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://access.redhat.com/errata/RHSA-2026:93618CNA: redhat · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:93622CNA: redhat · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/security/cve/CVE-2026-76166CNA: redhat · vdb-entry, x_refsource_REDHAT
- https://bugzilla.redhat.com/show_bug.cgi?id=2510883CNA: redhat · issue-tracking, x_refsource_REDHAT
For agents and automation
Read public disclosures for free as Markdown or JSON. Compatible browsers also expose native WebMCP tools to search disclosures, read this page, and discover API access.
Use the ontology-linked Cyber API with x402 pay per request, or a Y2 Pro or Elite API key with the intel:cyber scope.
Endpoints and access details
https://api.y2.dev/api/v2/cyber/cveshttps://api.y2.dev/api/v2/cyber/cves/{cveId}
A workspace owner or admin can create a Pro or Elite API key. Send Authorization: Bearer <Y2_API_KEY> from your trusted agent runtime.
For x402, omit Authorization and read the HTTP 402 payment challenge before signing a retry. Public browser tools do not make payments.