What is CVE-2026-9602?

CVE-2026-9602 is a medium-severity vulnerability in Mattermost, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2026-07-17.

How severe is CVE-2026-9602?

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

Resource exhaustion in Mattermost

CVE-2026-9602

Mattermost Desktop App versions <=6.2 6.0.2 5.6.13.0 fail to validate payloads sent from the Mattermost Web App to the Desktop App which allows a malicious server owner to crash the Mattermost Desktop App via changing the payload of a method to a malformed one. Mattermost Advisory ID: MMSA-2026-00678

Vulnerability class: DoS (Denial of Service)

Published 2026-07-17 · last modified 2026-10-15.

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 (34.9th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 34.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Mattermost — versions 0, 6.3.0, 6.2.1.0
Mattermost Desktop

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

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

Frequently asked questions

What is CVE-2026-9602?: CVE-2026-9602 is a medium-severity vulnerability in Mattermost, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2026-07-17.
How severe is CVE-2026-9602?: Medium severity. CVSS v3 base score is 6.5 out of 10.