What is CVE-2026-20719?

CVE-2026-20719 is a medium-severity vulnerability in Mattermost, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 4.3/10. Published 2026-03-25.

How severe is CVE-2026-20719?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Mattermost

CVE-2026-20719

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to prevent rendering of external SVGs on link embeds which allows unauthenticated users to crash the Mattermost webapp and desktop app via creating an issue or PR on GitHub.. Mattermost Advisory ID: MMSA-2026-00595

EPSS: 0.004 (27.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.

Affected products

Mattermost — versions 11.4.0, 11.3.0, 11.2.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-754 — Improper Check for Unusual or Exceptional Conditions

References

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

Frequently asked questions

What is CVE-2026-20719?: CVE-2026-20719 is a medium-severity vulnerability in Mattermost, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 4.3/10. Published 2026-03-25.
How severe is CVE-2026-20719?: Medium severity. CVSS v3 base score is 4.3 out of 10.