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CVE PROGRAM SOURCE RECORD4.3 Medium

CVE-2026-95666

Unbounded post ID array in the bulk reactions endpoint allows denial of service

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771

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

  • 11.9.0 to ≤ 11.9.1affected
  • 11.8.0 to ≤ 11.8.5affected
  • 11.7.0 to ≤ 11.7.10affected
  • 11.10.0 to ≤ 11.10.1affected
  • 11.11.0unaffected
  • 11.9.2unaffected
  • 11.8.6unaffected
  • 11.7.11unaffected
  • 11.10.2unaffected

References