Vulnerability DatabaseCVE-2026-4265
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CVE-2026-4265
March 16, 2026
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
Affected Packages
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost-server (GO):
Affected version(s) >=v11.3.0-rc1 <v11.3.1
Fix Suggestion:
Update to version v11.3.1
github.com/mattermost/mattermost/server/v8 (GO):
Affected version(s) >=v8.0.0-20230429093631-aac4f2337933 <v8.0.0-20260107144005-c7f6efdfb035
Fix Suggestion:
Update to version v8.0.0-20260107144005-c7f6efdfb035
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.3.0 <v11.3.1
Fix Suggestion:
Update to version v11.3.1
github.com/mattermost/mattermost-server (GO):
Affected version(s) >=v10.11.0-rc1 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost-server (GO):
Affected version(s) >=v11.2.0-rc1 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
Related Resources (5)
https://github.com/advisories/GHSA-xpvf-6qcc-9jqc
https://mattermost.com/security-updates
https://github.com/mattermost/mattermost/commit/c7f6efdfb035490f494b3177996ee5f4b278c988
https://nvd.nist.gov/vuln/detail/CVE-2026-4265
https://github.com/mattermost/mattermost
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CVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
CWE-863
EPSS
Base Score:
0.03