CVE-2025-13870: Unauthorized access and subscription vulnerability in Boards

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-02 · updated 2026-10-18
Weakness: CWE-306

Description

Mattermost versions 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate the user permission when accessing the files and subscribing to the block in Boards, which allows an authenticated user to access other board files and was able to subscribe to the block from other boards that the user does not have access to

Affected products

Mattermost: from 10.5.0 before 10.5.13; from 10.11.0 before 10.11.5 — fixed in 10.11.5, 10.5.13

How to fix

Upgrade to a fixed version: Mattermost 10.11.5, 10.5.13. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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