CVE-2026-20796

Summary

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

Affected Software

VendorProductVersion RangeStatus
MattermostMattermost10.11.0 <= 10.11.9affected
MattermostMattermost11.3.0unaffected
MattermostMattermost10.11.10unaffected

Weaknesses

  • CWE-367: CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

ADP Enrichment

CISA ADP Vulnrichment

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

References