Medium severity · published Apr 3, 2026
CVE-2026-28736
Focalboard IDOR in file content endpoint allows cross-user file access (unsupported product, no fix)
4.3
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FO
Focalboard · Mattermost
through 8.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28736
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-28736
Product
https://github.com/mattermost-community/focalboard
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