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

Published 2026-03-25 · last modified 2026-06-17.

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.

EPSS exploit prediction

EPSS: 0.004 (26.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 26.4% 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 11.4.0, 11.3.0, 11.2.0
Mattermost Server

Weakness classification (CWE)

CWE-754 — Improper Check for Unusual or Exceptional Conditions

References

mattermost.com/security-updates (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.