Skip to content
CVE PROGRAM SOURCE RECORD6.5 Medium

CVE-2026-6850

Crafted message attachment causes client-side denial of service via markdown parser regex backtracking in Mattermost

Read JSON ↗CVE.org ↗
Status
Published
Published
Updated
Assigning organization
Mattermost

Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658

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

  • 11.7.0 to ≤ 11.7.2affected
  • 11.6.0 to ≤ 11.6.4affected
  • 10.11.0 to ≤ 10.11.19affected
  • 11.8.0unaffected
  • 11.7.3unaffected
  • 11.6.5unaffected
  • 10.11.20unaffected

References