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CVE PROGRAM SOURCE RECORD7.1 High

CVE-2026-16453

Mattermost SAML RelayState forgery allows unauthorized team membership

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mattermost Mattermost

Default version status: unaffected

  • 11.10.0 to ≤ 11.10.0affected
  • 11.7.0 to ≤ 11.7.9affected
  • 11.9.0 to ≤ 11.9.1affected
  • 11.8.0 to ≤ 11.8.5affected
  • 11.11.0unaffected
  • 11.10.1unaffected
  • 11.7.10unaffected
  • 11.9.2unaffected
  • 11.8.6unaffected

References