What is CVE-2026-2457?

CVE-2026-2457 is a medium-severity vulnerability in Mattermost, classified under Origin Validation Error. CVSS score: 4.3/10. Published 2026-03-16.

How severe is CVE-2026-2457?

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

Vulnerability in Mattermost

CVE-2026-2457

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to sanitize client-supplied post metadata which allows an authenticated attacker to spoof permalink embeds impersonating other users via crafted PUT requests…

EPSS: 0.000 (6.6th 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:L/A:N.

Affected products

Mattermost — versions 11.3.0, 11.2.0, 10.11.0

Weakness classification (CWE)

CWE-346 — Origin Validation Error

References

MMSA-2025-00569 (vendor-advisory)

Frequently asked questions

What is CVE-2026-2457?: CVE-2026-2457 is a medium-severity vulnerability in Mattermost, classified under Origin Validation Error. CVSS score: 4.3/10. Published 2026-03-16.
How severe is CVE-2026-2457?: Medium severity. CVSS v3 base score is 4.3 out of 10.