What is CVE-2026-25783?

CVE-2026-25783 is a medium-severity vulnerability in Mattermost, classified under CWE-1287. CVSS score: 4.3/10. Published 2026-03-16.

How severe is CVE-2026-25783?

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

Vulnerability in Mattermost

CVE-2026-25783

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Matte…

EPSS: 0.001 (26.0th 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 11.3.0, 11.2.0, 10.11.0

Weakness classification (CWE)

CWE-1287

References

MMSA-2026-00586 (vendor-advisory)

Frequently asked questions

What is CVE-2026-25783?: CVE-2026-25783 is a medium-severity vulnerability in Mattermost, classified under CWE-1287. CVSS score: 4.3/10. Published 2026-03-16.
How severe is CVE-2026-25783?: Medium severity. CVSS v3 base score is 4.3 out of 10.