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CVE PROGRAM SOURCE RECORD4.3 Medium

CVE-2026-86349

Mattermost Server Algorithmic DoS via Unbounded Markdown Block Nesting

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.8, 10.11.x <= 10.11.22 fail to limit the nesting depth in the server-side Markdown parser which allows an authenticated attacker to cause a denial of service (CPU resource exhaustion) via a crafted post containing deeply nested blockquotes or list items.. Mattermost Advisory ID: MMSA-2026-00707

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 ≤ 11.9.0affected
  • 11.8.0 to ≤ 11.8.4affected
  • 11.7.0 to ≤ 11.7.8affected
  • 10.11.0 to ≤ 10.11.22affected
  • 11.10.0unaffected
  • 11.9.1unaffected
  • 11.8.5unaffected
  • 11.7.9unaffected
  • 10.11.23unaffected

References