CVE-2026-25783

CWE-12876 documents5 sources
Severity
4.3MEDIUM
EPSS
0.1%
top 78.73%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Github.com Mattermost/mattermost-serverGithub.com Mattermost/mattermost/server/v8Mattermost Mattermost Server+1 more
Timeline
PublishedMar 16
Latest updateMar 26

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:LExploitability: 2.8 | Impact: 1.4

Affected Packages4 packages

▶NVDmattermost/mattermost_server10.11.0 — 10.11.11+2
▶Gogithub.com/mattermost/mattermost-server10.11.0-rc1 — 10.11.11+6
▶Gogithub.com/mattermost/mattermost/server/v8< 8.0.0-20260129181235-1346cf529aef
▶CVEListV5mattermost/mattermost11.3.0 — 11.3.0+2

🔴Vulnerability Details

4
OSV
Mattermost fails to properly validate User-Agent header tokens in github.com/mattermost/mattermost-server↗2026-03-26
▶
OSV
Mattermost fails to properly validate User-Agent header tokens↗2026-03-16
▶
GHSA
Mattermost fails to properly validate User-Agent header tokens↗2026-03-16
▶
CVEList
Denial of service via malformed User-Agent header in getBrowserVersion↗2026-03-16
▶

🕵️Threat Intelligence

1
Wiz
CVE-2026-25783 Impact, Exploitability, and Mitigation Steps | Wiz↗
▶
CVE-2026-25783 (MEDIUM CVSS 4.3) | Mattermost versions 11.3.x <= 11.3. | cvebase.io