GHSA-2v3w-6g35-5f9vMediumCVSS 4.3

Mattermost fails to properly validate User-Agent header tokens

Published
March 16, 2026
Last Modified
March 17, 2026

🔗 CVE IDs covered (1)

CVE-2026-25783 →

📋 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

🎯 Affected products5

  • go/github.com/mattermost/mattermost/server/v8:< 8.0.0-20260129181235-1346cf529aef
  • go/github.com/mattermost/mattermost-server:< 5.3.2-0.20260129181235-1346cf529aef
  • go/github.com/mattermost/mattermost-server:>= 10.11.0-rc1, < 10.11.11
  • go/github.com/mattermost/mattermost-server:>= 11.2.0-rc1, < 11.2.3
  • go/github.com/mattermost/mattermost-server:>= 11.3.0-rc1, < 11.3.1

🔗 References (4)