Vulnerability DatabaseCVE-2026-86349
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CVE-2026-86349
Published:September 14, 2026
Updated:September 22, 2026
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 Packages
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) =v11.9.0 <v11.9.1
Fix Suggestion:
Update to version v11.9.1
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.7.0 <v11.7.9
Fix Suggestion:
Update to version v11.7.9
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.8.0 <v11.8.5
Fix Suggestion:
Update to version v11.8.5
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v10.11.0 <v10.11.23
Fix Suggestion:
Update to version v10.11.23
github.com/mattermost/mattermost/server/public (GO):
Affected version(s) >=v0.0.1 <v0.4.4
Fix Suggestion:
Update to version v0.4.4
Related Resources (1)
https://mattermost.com/security-updates
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CVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Weakness Type (CWE)
Inefficient Algorithmic Complexity
CWE-407
EPSS
Base Score:
0.22