What’s Vulnerable › Vulnerabilities

CVE-2024-39361: Creating posts with user-defined IDs permitted in CreatePost API

• Severity: medium (CVSS 5.4 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: 2024-07-03 · updated 2026-06-17
• Weakness: CWE-284

Description

Mattermost versions 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2 and 9.5.x <= 9.5.5 fail to prevent users from specifying a RemoteId for their posts which allows an attacker to specify both a remoteId and the post ID, resulting in creating a post with a user-defined post ID. This can cause some broken functionality in the channel or thread with user-defined posts

Affected products

• Mattermost App Framework: from 9.5.0 before 9.5.6; from 9.6.0 before 9.6.3; from 9.7.0 before 9.7.4; from 9.8.0 before 9.8.1 — fixed in 9.5.6, 9.6.3, 9.7.4, 9.8.1

How to fix

Upgrade to a fixed version: Mattermost App Framework 9.5.6, 9.6.3, 9.7.4, 9.8.1. Check the vendor advisory for mitigations.

References

• https://mattermost.com/security-updates
• https://mattermost.com/security-updates

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