CVE-2026-4273

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

Score

CVSS 3.1 4.3 Medium

Status

Analyzed - responsibledisclosure@mattermost.com

Published

2026-05-18

Last modified

2026-10-14

Weaknesses

CWE-863

Affected products

• Mattermost (Mattermost)
• Mattermost Server (Mattermost)

References

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