CVE-2024-36255: Post actions can run playbook checklist task commands

Severity: medium (CVSS 5.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-26 · updated 2026-06-17
Weakness: CWE-352

Description

Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1 and 8.1.x <= 8.1.12 fail to perform proper input validation on post actions which allows an attacker to run a playbook checklist task command as another user via creating and sharing a deceptive post action that unexpectedly runs a slash command in some arbitrary channel.

Affected products

Mattermost: from 8.1.0 before 8.1.13; from 9.5.0 before 9.5.4; from 9.6.0 before 9.6.2 — fixed in 8.1.13, 9.5.4, 9.6.2

How to fix

Upgrade to a fixed version: Mattermost 8.1.13, 9.5.4, 9.6.2. Check the vendor advisory for mitigations.

References

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