File Upload Permission Bypass in Mattermost Collaboration Software
CVE-2026-4265

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 March 2026

What is CVE-2026-4265?

A security vulnerability in Mattermost allows guest users to circumvent team-specific file upload permissions. By uploading files in a team where they do have upload permissions, malicious users can reuse the file metadata to post files in channels where they should lack such permissions. This flaw affects specific versions of Mattermost, making it crucial for users to update to secure their collaboration environments.

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Affected Version(s)

Mattermost 11.3.0

Mattermost 11.2.0 <= 11.2.2

Mattermost 10.11.0 <= 10.11.10

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

0x7oda7123
JSON
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