CVE-2026-25783

Summary

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 Software

VendorProductVersion RangeStatus
MattermostMattermost11.3.0 <= 11.3.0affected
MattermostMattermost11.2.0 <= 11.2.2affected
MattermostMattermost10.11.0 <= 10.11.10affected
MattermostMattermost11.4.0unaffected
MattermostMattermost11.3.1unaffected
MattermostMattermost11.2.3unaffected
MattermostMattermost10.11.11unaffected

Weaknesses

  • CWE-1287: CWE-1287: Improper Validation of Specified Type of Input

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References