Description
Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to properly apply markdown image rendering restrictions to AI bot tool result posts, which allows an authenticated attacker to exfiltrate data to an attacker-controlled server via injecting markdown image syntax into tool result content rendered by a victim's client.. Mattermost Advisory ID: MMSA-2026-00619
CVSS breakdown
CVSS 3.1
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None
Affected products
- Mattermost / Mattermost10.11.0 – 10.11.18
- Mattermost / Mattermost11.6.0 – 11.6.3
- Mattermost / Mattermost11.5.0 – 11.5.6
- Mattermost / Mattermost11.7.0 – 11.7.0
- Mattermost / Mattermost10.11.19 – 10.11.19
- Mattermost / Mattermost11.6.4 – 11.6.4
- Mattermost / Mattermost11.5.7 – 11.5.7