CVE-2026-6957 | BDVDB-2026-335261 Detail

MattermostMattermost

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

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact high. Attack vector: network.

Weaknesses#

CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

References#

https://mattermost.com/security-updates

Exploit#

No public exploit known

History#

Version 12026-05-27Record published in the CVE List.
Version 22026-05-28Most recent update recorded in the CVE List.

Published

Published: 2026-05-27
Last modified: 2026-05-28

Vendor information

Vendor: Mattermost
Product: Mattermost

All Mattermost vulnerabilities

Score

8.0 High

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 22.4.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Path Traversal

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
<= 1.1.5
Fixed
Not stated
Vulnerable
Not stated
Fixed
.0

Scoring System

CVSS v4.0

Not available

CVSS v3.1

8.0 High

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Metric breakdown
Attack Vector	Network
Attack Complexity	High
Privileges Required	High
User Interaction	None
Scope	Changed
Confidentiality	High
Integrity	High
Availability	High

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).