CVE-2026-6957

Path traversal in Mattermost Legal Hold plugin via unsanitized file name from federated peer allows arbitrary file write.

Published May 27, 2026 CVSS 3.1 · 8 High EPSS < 1% KEV · Not listed
Description
Mattermost Plugins versions <=1.1.5 fail to sanitize filenames received from federated peers before using them to construct export destination paths, which allows an administrator of a remote federated Mattermost server to write files to arbitrary locations within the target server's filestore via a malicious filename delivered through the shared-channel attachment sync protocol. Mattermost Advisory ID: MMSA-2026-00659

Remediation

Vendor Solution

Update Mattermost Plugins to versions .0 or higher.

Tracking

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Advisories

No advisories available
References
History
Type Values Removed Values Added
First Time appeared Mattermost legal Hold
CPEs cpe:2.3:a:mattermost:legal_hold:*:*:*:*:*:mattermost:*:*
Vendors & Products Mattermost legal Hold
Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Mattermost Plugins versions <=1.1.5 fail to sanitize filenames received from federated peers before using them to construct export destination paths, which allows an administrator of a remote federated Mattermost server to write files to arbitrary locations within the target server's filestore via a malicious filename delivered through the shared-channel attachment sync protocol. Mattermost Advisory ID: MMSA-2026-00659
Title Path traversal in Mattermost Legal Hold plugin via unsanitized file name from federated peer allows arbitrary file write.
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
May 28, 2026, 3:55 AM
Reserved
Apr 24, 2026, 1:23 PM
Status
Analyzed
Published
May 27, 2026, 3:16 PM
Modified
Jun 17, 2026, 11:01 AM