What is CVE-2026-10080?

CVE-2026-10080 is a medium-severity vulnerability in Mattermost, classified under Incorrect Type Conversion or Cast. CVSS score: 6.5/10. Published 2026-08-17.

How severe is CVE-2026-10080?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mattermost

CVE-2026-10080

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fails to validate WebSocket command field types which allows an authenticated user to crash the plugin process and deny service to all Boards users via a custom_focalboard_SUBSCRIBE_TEAM message with a non-string teamId.. Mattermost Advisory ID: MMSA-2026-00687

Published 2026-08-17 · last modified 2026-08-18.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.004 (34.0th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001

Affected products

Mattermost — versions 11.7.0, 10.11.0, 11.8.0
Mattermost Server

Weakness classification (CWE)

CWE-704 — Incorrect Type Conversion or Cast

References

mattermost.com/security-updates (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-10080?: CVE-2026-10080 is a medium-severity vulnerability in Mattermost, classified under Incorrect Type Conversion or Cast. CVSS score: 6.5/10. Published 2026-08-17.
How severe is CVE-2026-10080?: Medium severity. CVSS v3 base score is 6.5 out of 10.