# CVE-2026-76166: jws7-mod_cluster: A flaw was found in mod_cluster's AdvertiseListenerImpl (org.jboss.modcluster core module)

CVE-2026-76166 is fixed in 3 products on 1 platform, first by RHSA-2026:93618, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-76166
- Priority: Routine
- CVSS: 4.3 (moderate)
- EPSS: 0.0272
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 4, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | jws7-mod_cluster RHEL 10 | 2.1.1-1.Final_redhat_00001.1.el10jws | [RHSA-2026:93618](https://patchblox.com/security/data/fix/linux/rhsa-2026-93618.md) | Sep 23, 2026 |
| Linux | jws7-tomcat RHEL 10 | 11.0.21-10.redhat_00010.1.el10jws | [RHSA-2026:93618](https://patchblox.com/security/data/fix/linux/rhsa-2026-93618.md) | Sep 23, 2026 |
| Linux | jws7-tomcat-native RHEL 10 | 1.3.7-4.redhat_4.el10jws | [RHSA-2026:93618](https://patchblox.com/security/data/fix/linux/rhsa-2026-93618.md) | Sep 23, 2026 |

---

Data as of 2026-11-07T18:46:35Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.