CVE-2026-79534Hinoki check available

Out-of-boundary file writes via dangling symlinks

Published Sep 29, 2026 · Updated Sep 29, 2026

Directory traversal in Mark III Labs MCP Filesystem Server 0.11.1 allows attackers to write outside allowed directories through dangling symlinks. In validatePath, a failed EvalSymlinks call for a nonexistent target checks only the parent directory and returns the unresolved path to file-writing tools. Exploitation requires access to an MCP file operation and a pre-existing dangling symlink inside an allowed directory; writes remain limited by the server process's filesystem permissions.

CVSS severityUnavailable
Unscored
EPSS probability0.19%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Directory traversal in Mark III Labs MCP Filesystem Server 0.11.1 allows attackers to write outside allowed directories through dangling symlinks. In validatePath, a failed EvalSymlinks call for a nonexistent target checks only the parent directory and returns the unresolved path to file-writing tools. Exploitation requires access to an MCP file operation and a pre-existing dangling symlink inside an allowed directory; writes remain limited by the server process's filesystem permissions.

The record

CVE
CVE-2026-79534
Published
Sep 29, 2026
Updated
Sep 29, 2026
Vendor
Mark III Labs
Product
MCP Filesystem Server
Classifications
T1565.001
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Mark III Labs · MCP Filesystem Serverversion=n/a

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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