Arbitrary Markdown file operations via unchecked path joins
Published Sep 7, 2026 · Updated Sep 8, 2026
Path traversal in Knowns before 0.30.0 allows remote authenticated users to read, create, overwrite, or delete Markdown files. DocStore and MemoryStore join MCP-supplied path, folder, newPath, and id values to managed roots with filepath.Join, then perform filesystem operations without confirming that the resolved path remains inside those roots. Low-privilege MCP access and no user interaction are required; affected operations reach only Markdown files accessible to the server process, while docs.update can bypass a no-delete preset through its rename path.
Summary
What happened
Path traversal in Knowns before 0.30.0 allows remote authenticated users to read, create, overwrite, or delete Markdown files. DocStore and MemoryStore join MCP-supplied path, folder, newPath, and id values to managed roots with filepath.Join, then perform filesystem operations without confirming that the resolved path remains inside those roots. Low-privilege MCP access and no user interaction are required; affected operations reach only Markdown files accessible to the server process, while docs.update can bypass a no-delete preset through its rename path.
The record
- CVE
- CVE-2026-86439
- Published
- Sep 7, 2026
- Updated
- Sep 8, 2026
- Vendor
- Knowns
- Product
- Knowns
- Classifications
- CWE-22, CWE-863
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 7, 2026CVE publishedPublication date reported by the CVE source.
- Sep 8, 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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- Affected versionversion=0 <0.30.0
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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