CVE-2025-9081: IDOR in board file download allows any user to download any file by UUID

Severity: medium (CVSS 6.5 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: 2025-09-19 · updated 2026-10-19
Weakness: CWE-639

Description

Mattermost versions 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate access controls which allows any authenticated user to download sensitive files via board file download endpoint using UUID enumeration

Affected products

Mattermost: from 9.11.0 before 9.11.17; from 10.5.0 before 10.5.9 — fixed in 10.5.9, 9.11.17

How to fix

Upgrade to a fixed version: Mattermost 10.5.9, 9.11.17. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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