PT-2026-25705 · Mattermost · Mattermost

0X7Oda7123 · Published 2026-03-16 · Updated 2026-03-16 · CVE-2026-4265

Mitre

CVSS v3.1

4.3

4.3

Medium

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

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

Fix

Incorrect Authorization

Weakness Enumeration

CWE-863

Related Identifiers

CVE-2026-4265

Affected Products

Mattermost

References · 3

• https://mattermost.com/security-updates · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4265 · Security Note
• https://twitter.com/CVEnew/status/2033583645269889149 · Twitter Post