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CVE PROGRAM SOURCE RECORD6.5 Medium

CVE-2026-5163

Missing authorization check in AI message rewrite endpoint allows access to private thread content

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645

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

  • 11.5.0 to ≤ 11.5.1affected
  • 11.6.0unaffected
  • 11.5.2unaffected

References