CVE-2024-39830: Timing attack during remote cluster token comparison when shared channels are enabled

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% 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-287

Description

Mattermost versions 9.8.x <= 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2 and 9.5.x <= 9.5.5, when shared channels are enabled, fail to use constant time comparison for remote cluster tokens which allows an attacker to retrieve the remote cluster token via a timing attack during remote cluster token comparison.

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 9.7.5; from 9.8.0 before 9.8.1 — fixed in 9.5.6, 9.6.3, 9.7.5, 9.8.1

How to fix

Upgrade to a fixed version: Mattermost App Framework 9.5.6, 9.6.3, 9.7.5, 9.8.1. Check the vendor advisory for mitigations.

References

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