CVE-2026-86439: Unrestricted Path Traversal in Known's MCP Docs and Memory Tools
Summary
CVE-2026-86439: Overview Verified. Affects knowns versions < 0.30.0. Fixed in 0.30.0. How to fix ↓
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Background
Known's MCP is a set of tools designed for managing documents and memory entries within a project. It allows users to create, read, update, and delete files efficiently. However, it has been identified that the MCP Docs and Memory Tools are vulnerable to unrestricted path traversal, which can lead to unauthorized file access and manipulation.
Vulnerability Detail
The vulnerability arises from multiple unrestricted path traversal flaws in the Knowns MCP's storage layer, specifically in the doc_store.go and memory_store.go files. These flaws allow attackers to read, write, and delete files outside the intended project directory by manipulating user-controlled paths. The lack of proper containment checks when constructing file paths using filepath.Join() enables attackers to exploit this vulnerability. Additionally, an authorization bypass exists where the docs.update action can delete files without the necessary permissions, further exacerbating the risk.
How To Fix
Minimum fixed version
0.30.0
This is the first release that contains the fix.
npm install knowns@0.30.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, ensure that user inputs for file paths are sanitized and validated before being processed. Implement checks to reject any paths that contain traversal sequences (e.g., '..') or absolute paths.
Conclusion
The CVE-2026-86439 vulnerability in Known's MCP poses serious risks due to unrestricted path traversal and authorization bypass. It is crucial to update to the patched version to mitigate these risks and ensure the security of your application.
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FAQ
CVE-2026-86439 is a vulnerability in Known's MCP that allows unrestricted path traversal, leading to unauthorized file access and manipulation.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
The vulnerability can lead to arbitrary file read, write, and deletion operations outside the project directory, posing significant security risks.
You can update the Known's package by running 'npm install knowns@0.30.0' in your project directory to apply the necessary patches.
The CVSS score of this vulnerability is 8.8, indicating a high severity level.
References
Related vulnerabilities
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