Quick answers
- Is CVE-2026-6957 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-6957 being exploited in the wild.
- How severe is CVE-2026-6957?
- High severity, with a CVSS score of 8, published 27 May 2026.
- Which products and versions are affected?
- Mattermost Plugins <=1.1.5.
- Is there a fix for CVE-2026-6957?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-6957 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-6957?
- Check whether you run Mattermost Plugins at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A path traversal vulnerability (CWE-22) exists in Mattermost Plugins versions <=1.1.5 due to insufficient sanitization of filenames received from federated peers. The vulnerability is triggered during the shared-channel attachment sync protocol when the plugin uses unsanitized filenames to construct export destination paths. An attacker with administrative privileges on a remote federated Mattermost server can provide a malicious filename containing traversal sequences (e.g., ../) to write files to arbitrary locations within the target server's filestore. While the attack requires high privileges (PR:H) and specific configuration (federation), the impact is significant as it crosses security boundaries (S:C).
Affected products
- Mattermost Mattermost Plugins <=1.1.5
Timeline
- 2026-05-27: disclosed: CVE-2026-6957 published by NVD and Mattermost