What is CVE-2026-9699?

CVE-2026-9699 is a medium-severity vulnerability in Mattermost, classified under Insertion of Sensitive Information into Log File. CVSS score: 6.8/10. Published 2026-06-26.

How severe is CVE-2026-9699?

Medium severity. CVSS v3 base score is 6.8 out of 10.

Information disclosure in Mattermost

CVE-2026-9699

Mattermost Plugins versions <=11.6 10.18.11 11.3.6 11.6.5.0 fail to sanitize error responses from the OpenAI API before logging, which allows a user with access to server logs or support packets to obtain a valid or partially reconstructab…

CVSS v3 metric

CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N.

Affected products

Mattermost — versions 0, 11.7.0, 10.11.19

Weakness classification (CWE)

CWE-532 — Insertion of Sensitive Information into Log File

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-9699?: CVE-2026-9699 is a medium-severity vulnerability in Mattermost, classified under Insertion of Sensitive Information into Log File. CVSS score: 6.8/10. Published 2026-06-26.
How severe is CVE-2026-9699?: Medium severity. CVSS v3 base score is 6.8 out of 10.