CVE-2026-28736

MEDIUM 4.3

Focalboard IDOR in file content endpoint allows cross-user file access (unsupported product, no fix)

CVSS Score

4.3

EPSS Score

0.0%

EPSS Percentile

0th

** 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.

CWE	CWE-639
Vendor	mattermost
Product	focalboard
Published	Apr 3, 2026
Last Updated	Apr 3, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Affected Versions

Mattermost / Focalboard

0 ≤ 8.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/mattermost-community/focalboard

Credits

Siam Thanat Hack Company Limited