CVE-2026-3472 Markdown image rendering bypass in AI bot tool result posts in Mattermost
An authenticated attacker can exfiltrate data to an external server by injecting markdown image syntax into AI bot tool result posts rendered by victims.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-3472?
CVE-2026-3472 is a low-severity vulnerability in Mattermost Mattermost Server, published on 26 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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
Weakness: CWE-693
Which versions are affected by CVE-2026-3472?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-3472?
No fix has been published for CVE-2026-3472 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-3472 being exploited?
There is no known exploitation of CVE-2026-3472 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as GHSA-8rm3-f79m-54wg.