CVE-2026-4273: Insufficient token rotation validation in remote cluster invite confirmation
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a crafted invite confirmation with a RefreshedToken matching the original token. Mattermost Advisory ID: MMSA-2026-00575
Affected Software
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Event History
Frequently Asked Questions
What is the severity of CVE-2026-4273?
The severity of CVE-2026-4273 is considered high due to the potential for exploitation by authenticated attackers.
How do I fix CVE-2026-4273?
To fix CVE-2026-4273, upgrade Mattermost to version 11.5.2 or 10.11.14 or later where the issue has been addressed.
What systems are affected by CVE-2026-4273?
CVE-2026-4273 affects Mattermost versions 11.5.0 to 11.5.1 and 10.11.0 to 10.11.13.
What is the nature of the vulnerability in CVE-2026-4273?
CVE-2026-4273 is an insufficient token rotation validation vulnerability that can allow an authenticated attacker to exploit remote cluster invite confirmations.
Can CVE-2026-4273 be exploited without authentication?
No, CVE-2026-4273 requires authentication as the vulnerability can only be exploited by authenticated users.