CVE-2026-6957

Name: CVE-2026-6957
Creator: NVD / NIST
Published: 2026-05-27T15:16:34.903+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.9/10EPSS 0.30%

Last modified Jun 17, 2026

CVE-2026-6957 is a medium-severity vulnerability rated 4.9/10 on the CVSS scale. 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. EPSS estimates a 0.30% chance of exploitation in the next 30 days.

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

Metrics

CVSS 3.1

4.9/10

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

EPSS Probability

0.30%

21.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-22

Affected Software

Vendor	Product	Versions
Mattermost	Legal Hold	<= 1.1.5

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: May 27, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-6957?

How severe is CVE-2026-6957?

CVE-2026-6957 has a CVSS score of 4.9/10 (MEDIUM severity). The EPSS model estimates a 0.30% probability of exploitation in the next 30 days.

How do I fix CVE-2026-6957?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-6957?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST