What is CVE-2026-12666?

CVE-2026-12666 is a high-severity vulnerability in IBM Mq, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 8.1/10. Published 2026-09-15.

How severe is CVE-2026-12666?

High severity. CVSS v3 base score is 8.1 out of 10.

XXE in IBM Mq

CVE-2026-12666

IBM MQ 9.1.0.0 through 9.1.0.37 LTS, 9.2.0.0 through 9.2.0.43 LTS, 9.3.0.0 through 9.3.0.41 LTS, 9.3.0.0 through 9.3.5.1 CD, 9.4.0.0 through 9.4.0.25 LTS, 9.4.0.0 through 9.4.5.1 CD, and 10.0.0.0 Classes for Java could allow an authenticated attacker to obtain sensitive information or cause a denial of service due to XML external entity injection in MQRFH2 header processing.

Vulnerability class: XXE (XML External Entity)

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H.

Affected products

Ibm Mq — versions 10.0.0.0

Weakness classification (CWE)

CWE-611 — Improper Restriction of XML External Entity Reference (XXE)

References

psirt@us.ibm.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-12666?: CVE-2026-12666 is a high-severity vulnerability in IBM Mq, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 8.1/10. Published 2026-09-15.
How severe is CVE-2026-12666?: High severity. CVSS v3 base score is 8.1 out of 10.