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CVE-2026-6957

8.0 · HIGH

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 feder…

Published May 27, 2026mattermostCWE-22EPSS 0.30%

Overview

CVE-2026-6957 is a high-severity vulnerability affecting mattermost legal_hold. It was published on May 27, 2026 and has a CVSS 3.1 base score of 8.0 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.0, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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

Check the references section for vendor advisories and patches from mattermost. Update legal_hold to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
mattermostlegal_hold0Affected

References

Refmattermost.com/security-updates

How CyberStrike helps

Frequently asked questions

What is CVE-2026-6957?

CVE-2026-6957 is a high-severity vulnerability affecting mattermost legal_hold. It was published on May 27, 2026 and has a CVSS 3.1 base score of 8.0 (HIGH).

How severe is CVE-2026-6957?

This vulnerability has a CVSS 3.1 base score of 8.0, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-6957?

Check the references section for vendor advisories and patches from mattermost. Update legal_hold to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-6957?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-6957 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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