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CVE PROGRAM SOURCE RECORD7.5 High

CVE-2026-5740

Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647

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

  • 11.6.0 to ≤ 11.6.0affected
  • 11.5.0 to ≤ 11.5.3affected
  • 11.4.0 to ≤ 11.4.4affected
  • 10.11.0 to ≤ 10.11.14affected
  • 11.7.0unaffected
  • 11.6.1unaffected
  • 11.5.4unaffected
  • 11.4.5unaffected
  • 10.11.15unaffected

References