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

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-xpvf-6qcc-9jqc Mattermost fails to validate team-specific upload_file permissions
Fixes

Solution

Update Mattermost to versions 11.4.0, 11.3.1, 11.2.3, 10.11.11 or higher.


Workaround

No workaround given by the vendor.

References
History

Wed, 18 Mar 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost
Mattermost mattermost Server

Mon, 16 Mar 2026 14:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 16 Mar 2026 12:15:00 +0000

Type Values Removed Values Added
Description 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
Title Guest user can upload files without permission across teams
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-03-16T13:49:55.080Z

Reserved: 2026-03-16T12:05:32.172Z

Link: CVE-2026-4265

cve-icon Vulnrichment

Updated: 2026-03-16T13:43:37.311Z

cve-icon NVD

Status : Analyzed

Published: 2026-03-16T14:20:19.733

Modified: 2026-03-18T17:41:56.197

Link: CVE-2026-4265

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses