CVE-2026-86349

Summary

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 Software

VendorProductVersion RangeStatus
MattermostMattermost11.9.0 <= 11.9.0affected
MattermostMattermost11.8.0 <= 11.8.4affected
MattermostMattermost11.7.0 <= 11.7.8affected
MattermostMattermost10.11.0 <= 10.11.22affected
MattermostMattermost11.10.0unaffected
MattermostMattermost11.9.1unaffected
MattermostMattermost11.8.5unaffected
MattermostMattermost11.7.9unaffected
MattermostMattermost10.11.23unaffected

Weaknesses

  • CWE-407: CWE-407: Inefficient Algorithmic Complexity

ADP Enrichment

CISA ADP Vulnrichment

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

References