CVE-2026-3108: Terminal Escape Injection in mmctl Report Posts Command

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-26 · updated 2026-06-17
Weakness: CWE-150

Description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599

Affected products

Mattermost: from 10.11.0 before 10.11.11; from 11.2.0 before 11.2.3; from 11.3.0 before 11.3.2; 11.4.0 — fixed in 10.11.11, 11.2.3, 11.3.2

How to fix

Upgrade to a fixed version: Mattermost 10.11.11, 11.2.3, 11.3.2. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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