CVE-2026-4265 — Incorrect Authorization in Mattermost Mattermost-server

CWE-863 — Incorrect Authorization6 documents5 sources
Severity
4.3MEDIUMNVD
EPSS
0.0%
top 92.98%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Github.com Mattermost Mattermost-serverGithub.com Mattermost Mattermost Server V8Mattermost Server+1 more
Timeline
PublishedMar 16
Latest updateMar 23

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:NExploitability: 2.8 | Impact: 1.4

Affected Packages4 packages

▶NVDmattermost/mattermost_server10.11.0 — 10.11.11+2
▶Gogithub.com/mattermost_mattermost-server10.11.0-rc1+incompatible — 10.11.11+incompatible+6
▶Gogithub.com/mattermost_mattermost_server_v8< 8.0.0-20260107144005-c7f6efdfb035
▶CVEListV5mattermost/mattermost11.3.0 — 11.3.0+2

🔴Vulnerability Details

4
OSV
Mattermost fails to validate team-specific upload_file permissions in github.com/mattermost/mattermost-server↗2026-03-23
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OSV
Mattermost fails to validate team-specific upload_file permissions↗2026-03-16
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CVEList
Guest user can upload files without permission across teams↗2026-03-16
▶
GHSA
Mattermost fails to validate team-specific upload_file permissions↗2026-03-16
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🕵️Threat Intelligence

1
Wiz
CVE-2026-4265 Impact, Exploitability, and Mitigation Steps | Wiz↗
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