CVE-2026-28736
Received Received - Intake
Insecure File Access in Focalboard 8.0 Allows Unauthorized Reading

Publication date: 2026-04-03

Last updated on: 2026-04-28

Assigner: Mattermost, Inc.

Description
** UNSUPPORTED WHEN ASSIGNED ** Focalboard version 8.0 fails to validate file ownership when serving uploaded files. This allows an authenticated attacker who knows a victim's fileID to read the content of the file. NOTE: Focalboard as a standalone product is not maintained and no fix will be issued.
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Meta Information
Published
2026-04-03
Last Modified
2026-04-28
Generated
2026-06-16
AI Q&A
2026-04-03
EPSS Evaluated
2026-06-15
NVD
CVE-2026-28736
EUVD
EUVD-2026-18653
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
mattermost focalboard 8.0.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-639 The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
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Executive Summary

Focalboard version 8.0 has a vulnerability where it fails to validate file ownership when serving uploaded files. This means that an authenticated attacker who knows the fileID of a victim's file can read the content of that file without proper authorization.

Impact Analysis

This vulnerability allows an authenticated attacker to access and read files belonging to other users if they know the fileID. This can lead to unauthorized disclosure of potentially sensitive or confidential information.

Mitigation Strategies

Focalboard as a standalone product is not maintained and no fix will be issued for this vulnerability.

Given this, immediate mitigation steps are limited. It is recommended to restrict authenticated user access to file IDs and monitor for unauthorized file access attempts.

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