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CVE-2026-3473

Improper file ownership validation in the Boards API allows unauthorised file access

Published: May 22, 2026Updated: May 22, 2026 Sources: CVE List BDUCWE-639CWE-639: Authorization Bypass Through User-Controlled Key
5.9MEDIUM
NVD MITRE
EPSS Score
0.1%
Top 95.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:LUI:NS:UC:HI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-639CWE-639: Authorization Bypass Through User-Controlled Key

Affected Products

Mattermost
commercial·US
MattermostOn-premWeb App
Communications / messaging-chat
Mattermost Inc
commercial·USaka mattermost
MattermostOn-premWeb App
Communications / messaging-chat

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Initial Access
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References

https://mattermost.com/security-updates
mattermost.com
https://mattermost.com/security-updates&#13;
mattermost.com
https://feedly.com/cve/CVE-2026-3473&#13;
feedly.com
and 1 more references View all →
News mentions
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