What is CVE-2026-1628?

CVE-2026-1628 is a medium-severity vulnerability in Mattermost, classified under Inclusion of Functionality from Untrusted Control Sphere. CVSS score: 4.6/10. Published 2026-03-02.

How severe is CVE-2026-1628?

Medium severity. CVSS v3 base score is 4.6 out of 10.

Vulnerability in Mattermost

CVE-2026-1628

Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596

Published 2026-03-02 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.001 (3.3th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 3rd percentile — 3.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: +0.000

Affected products

Mattermost — versions 0, 5.13.4.0
Mattermost Desktop

Weakness classification (CWE)

CWE-829 — Inclusion of Functionality from Untrusted Control Sphere

References

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

Frequently asked questions

What is CVE-2026-1628?: CVE-2026-1628 is a medium-severity vulnerability in Mattermost, classified under Inclusion of Functionality from Untrusted Control Sphere. CVSS score: 4.6/10. Published 2026-03-02.
How severe is CVE-2026-1628?: Medium severity. CVSS v3 base score is 4.6 out of 10.