Vulnerability · Published Jun 26, 2026 · Assigned by Mattermost

CVE-2026-3472Markdown image rendering bypass in AI bot tool result posts in Mattermost

Low 3.5

In plain English

A low-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).

Severity (CVSS 3.1)3.5Low

Exploit odds (30 days)0.3%top 80.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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

Affected products (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	10.11.0 – through 10.11.1811.6.0 – through 11.6.311.5.0 – through 11.5.6

Weakness: CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N

References

MMSA-2026-00619 vendor-advisory