# CVE-2026-12343: IBM MQ denial of service in RFH2 message header validation

Source: https://junglewise.ai/threats/cve-2026-12343-ibm-mq-could-allow-an-authenticated-attacker-to-cause-a-denial-of  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-19. Updated: 2026-10-19  
License: CC BY 4.0 with a link back

CVE-2026-12343 · Severity: medium · CVSS 6.5 · Published 2026-10-19

IBM MQ is a message queuing system used by enterprises to reliably transmit data between applications. An authenticated attacker can send specially crafted messages with invalid RFH2 header fields that cause the message queue to crash, disrupting message delivery and application communication.

Technologies: [IBM Mq](https://junglewise.ai/threats/technologies/mq). Vendors: [IBM](https://junglewise.ai/threats/vendors/ibm).

## Quick answers

**Is CVE-2026-12343 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-12343 being exploited in the wild.

**How severe is CVE-2026-12343?** Medium severity, with a CVSS score of 6.5, published 19 October 2026.

**Which products and versions are affected?** IBM MQ.

**Is there a fix for CVE-2026-12343?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-12343 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-12343?** Check whether you run IBM Mq. 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.

## Technical details

The vulnerability exists in the RFH2 message header validation logic in IBM MQ's publish/subscribe operations. An authenticated attacker can provide malformed RFH2 header field values that fail validation, leading to improper error handling that causes a denial of service. The attack requires prior authentication to the message queue.

## Affected products

- IBM MQ

## Timeline

- 2026-10-19: disclosed

## References

- [https://www.ibm.com/support/pages/node/7292667](https://www.ibm.com/support/pages/node/7292667)

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