Cyber Posture

CVE-2026-6957

High
Microsoft: not affectedMSmacOS: not affectedMacLinux: not affectedLnxMobile: not affectedMobNetwork: not affectedNetApplication: not affectedAppOther: affectedOth

Published: 27 May 2026

Published
27 May 2026
Modified
27 May 2026
KEV Added
—
Patch
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CVSS Score 8.0 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
EPSS Score 0.0004 13.5th percentile
Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-6957 is a high-severity Path Traversal (CWE-22) vulnerability in Mattermost Plugins (inferred from references). Its CVSS base score is 8.0 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 13.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique.
Threat & Defense Details

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-10 Information Input Validation
addresses: CWE-22

Validates pathnames and filenames to prevent traversal outside intended directories.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1105 Ingress Tool Transfer Command And Control
Adversaries may transfer tools or other files from an external system into a compromised environment.
attack.mitre.org →
Why these techniques?

Path traversal (CWE-22) in federated sync protocol directly enables remote arbitrary file write, mapping to exploitation of the server application and ingress of attacker-controlled files.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD 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…

more

filestore via a malicious filename delivered through the shared-channel attachment sync protocol. Mattermost Advisory ID: MMSA-2026-00659

Deeper analysisAI

Automated synthesis unavailable for this CVE.

Details

CWE(s)
CWE-22
OWASP Top 10 Web 2025
A01:2025

Affected Products

Mattermost
Plugins
inferred from references and description; NVD did not file a CPE for this CVE

EU & UK References

References