What is CVE-2026-5308?

CVE-2026-5308 is a medium-severity vulnerability in Mattermost, classified under Uncontrolled Resource Consumption. CVSS score: 4.9/10. Published 2026-05-22.

How severe is CVE-2026-5308?

Medium severity. CVSS v3 base score is 4.9 out of 10.

Resource exhaustion in Mattermost

CVE-2026-5308

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to enforce request body size limits on plugin HTTP endpoints which allows an attacker to cause a denial of service via crafted oversized HTT…

Vulnerability class: DoS (Denial of Service)

EPSS: 0.001 (16.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H.

Affected products

Mattermost — versions 11.6.0, 11.5.0, 11.4.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-5308?: CVE-2026-5308 is a medium-severity vulnerability in Mattermost, classified under Uncontrolled Resource Consumption. CVSS score: 4.9/10. Published 2026-05-22.
How severe is CVE-2026-5308?: Medium severity. CVSS v3 base score is 4.9 out of 10.