CVE-2026-4265

Guest user can upload files without permission across teams

State: Published
Severity: 4.3 Medium
Published: Mar 16, 2026
Updated: Mar 16, 2026
Reserved: Mar 16, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N	Mattermost

Weaknesses

CWE-863 Incorrect Authorization

Affected Products

Product	Versions
MattermostMattermost	11.3.0 through 11.3.0Affected 11.2.0 through 11.2.2Affected 10.11.0 through 10.11.10Affected 11.4.0Not affected 11.3.1Not affected 11.2.3Not affected 10.11.11Not affected

References

MMSA-2025-00553vendor-advisory

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