Focalboard 8.0 Auth File Read via File Ownership Bypass
CVE-2026-28736 Published on April 3, 2026
Focalboard IDOR in file content endpoint allows cross-user file access (unsupported product, no fix)
** 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.
Vulnerability Analysis
CVE-2026-28736 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Weakness Type
What is an Insecure Direct Object Reference / IDOR Vulnerability?
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.
CVE-2026-28736 has been classified to as an Insecure Direct Object Reference / IDOR vulnerability or weakness.
Affected Versions
Mattermost Focalboard:- Before and including 8.0 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.