CVE-2025-3446: Members Without Guest Invite Permissions Can Add Guests to Teams

Severity: medium (CVSS 4.3 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: 2025-05-15 · updated 2026-06-17
Weakness: CWE-863

Description

Mattermost versions 10.6.x <= 10.6.1, 10.5.x <= 10.5.2, 10.4.x <= 10.4.4, 9.11.x <= 9.11.11 fail to check the correct permissions which allows authenticated users who only have permission to invite non-guest users to a team to add guest users to that team via the API to add a single user to a team.

Affected products

Mattermost: from 9.11.0 before 9.11.12; from 10.4.0 before 10.4.5; from 10.5.0 before 10.5.3; from 10.6.0 before 10.6.2 — fixed in 10.4.5, 10.5.3, 10.6.2, 9.11.12

How to fix

Upgrade to a fixed version: Mattermost 10.4.5, 10.5.3, 10.6.2, 9.11.12. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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