# CVE-2026-111821: Apache ActiveMQ improper input validation in durable subscriptions

Source: https://junglewise.ai/threats/cve-2026-111821-improper-input-validation-vulnerability-in-apache-activemq  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-111821 · Severity: info · Published 2026-11-04

Apache ActiveMQ is a message broker used to route and deliver messages in distributed applications. A flaw in input validation allows an attacker to create a durable subscription with combined identifiers exceeding 65,535 characters, causing the broker to shut down unexpectedly and become unrecoverable. This results in a denial of service affecting all applications relying on the broker.

Technologies: [Apache ActiveMQ](https://junglewise.ai/threats/technologies/activemq). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-111821 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-111821 being exploited in the wild.

**How severe is CVE-2026-111821?** Informational severity, published 4 November 2026.

**Which products and versions are affected?** Apache ActiveMQ 6.0.0 to before 6.3.3, 5.x before 5.19.12; Apache ActiveMQ KahaDB 6.0.0 to before 6.3.3, 5.x before 5.19.12.

**Is there a fix for CVE-2026-111821?** Yes: fixed in ActiveMQ 6.4.0, 6.3.3, 5.19.12. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-111821 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-111821?** Check whether you run Apache ActiveMQ or Apache ActiveMQ KahaDB at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in ActiveMQ 6.4.0, 6.3.3, 5.19.12

## Technical details

The vulnerability is an improper input validation flaw in ActiveMQ's KahaDB persistence layer. An attacker can craft a durable subscription request where the clientId and subscription name, when combined, exceed 65,535 characters (while each individually stays below limits), triggering a broker crash. The issue requires network access to the broker and the ability to create subscriptions; no authentication bypass is involved.

## Affected products

- Apache ActiveMQ 6.0.0 to before 6.3.3, 5.x before 5.19.12
- Apache ActiveMQ KahaDB 6.0.0 to before 6.3.3, 5.x before 5.19.12

## Timeline

- 2026-11-04: disclosed

## References

- [https://repo.maven.apache.org/maven2](https://repo.maven.apache.org/maven2)
- [https://lists.apache.org/thread/p8gxq66lmztkrls74wkz3xh9chqd0pwl](https://lists.apache.org/thread/p8gxq66lmztkrls74wkz3xh9chqd0pwl)

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