CVE-2026-4265 — Guest user can upload files without permission across teams
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 cha…
Published: 2026-03-16 · CVSS: 4.3 · CVSS 3.1
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
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7