CVE-2026-25783

Denial of service via malformed User-Agent header in getBrowserVersion

State: Published
Severity: 4.3 Medium
Published: Mar 16, 2026
Updated: Mar 16, 2026
Reserved: Feb 13, 2026

Description

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

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L	Mattermost

Weaknesses

CWE-1287 Improper Validation of Specified Type of Input

Affected Products

Product	Versions
MattermostMattermost	11.3.0 through 11.3.0Affected 11.2.0 through 11.2.2Affected 10.11.0 through 10.11.10Affected 11.4.0Not affected 11.3.1Not affected 11.2.3Not affected 10.11.11Not affected

References

MMSA-2026-00586vendor-advisory

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