CVE-2024-36257: Lack of permission check when updating the profile picture of a remote user (shared channels enabled)

Severity: medium (CVSS 5.3 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 9.5.x <= 9.5.5 and 9.8.0, when using shared channels with multiple remote servers connected, fail to check that the remote server A requesting the server B to update the profile picture of a user is the remote that actually has the user as a local one . This allows a malicious remote A to change the profile images of users that belong to another remote server C that is connected to the server A.

Affected products

Mattermost App Framework: from 9.5.0 before 9.5.6; 9.8.0 — fixed in 9.5.6

How to fix

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

References

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