GitHub Advisoryadvisory · Go

GHSA-xpvf-6qcc-9jqc Mattermost fails to validate team-specific upload_file permissions

MEDIUM Published 2026-03-16 Modified 2026-03-18 Official page ↗
Aliases
CVE-2026-4265
Ecosystem
Go
Packages
github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Weaknesses
CWE-863
Reviewed
2026-03-18

Affected packages

• Go github.com/mattermost/mattermost/server/v8: < 8.0.0-20260107144005-c7f6efdfb035 → fixed in 8.0.0-20260107144005-c7f6efdfb035 • Go github.com/mattermost/mattermost-server: < 5.3.2-0.20260107144005-c7f6efdfb035 → fixed in 5.3.2-0.20260107144005-c7f6efdfb035 • Go github.com/mattermost/mattermost-server: >= 10.11.0-rc1, < 10.11.11 → fixed in 10.11.11 • Go github.com/mattermost/mattermost-server: >= 11.2.0-rc1, < 11.2.3 → fixed in 11.2.3 • Go github.com/mattermost/mattermost-server: >= 11.3.0-rc1, < 11.3.1 → fixed in 11.3.1

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

Related

Alias · CVE (1)

  • CVE-2026-4265 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… vulnerability

Weakness · CWE (1)

  • CWE-863 Incorrect Authorization weakness

References