Markdown Rendering Flaw in Mattermost Affects Versions 10.11.x, 11.6.x, and 11.5.x
CVE-2026-3472

3.5LOW

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
26 June 2026

What is CVE-2026-3472?

A security issue in Mattermost has been identified where certain versions do not adequately restrict markdown image rendering in AI bot tool results. This flaw enables authenticated attackers to inject markdown image syntax, potentially allowing sensitive data to be exfiltrated to an external server controlled by the attacker. Users should promptly verify their Mattermost versions and apply available patches to mitigate this risk. More details can be found in the Mattermost Advisory ID: MMSA-2026-00619.

Affected Version(s)

Mattermost 10.11.0 <= 10.11.18

Mattermost 11.6.0 <= 11.6.3

Mattermost 11.5.0 <= 11.5.6

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
3.5
Severity:
LOW
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Juho Forsén
.