CVE-2026-25783 MEDIUM

CVE-2026-25783: Denial of service via malformed User-Agent header in getBrowserVersion

Vendor Mattermost
Product Mattermost
Weakness CWE-1287
Published March 16, 2026
Last update March 16, 2026
View on NVD All CVEs

CVSS base score

4.3/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

What the vulnerability does

01Description

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. Mattermost Advisory ID: MMSA-2026-00586

Key dates

02Disclosure timeline

March 16, 2026 CVE published
March 16, 2026 Record updated