CVE-2026-81486 in mcp-file-context-server
Summary
by MITRE • 08/27/2026
A vulnerability was detected in bsmi021 mcp-file-context-server 1.0.0. Affected by this issue is the function read_context of the file src/index.ts of the component Path Resolution. Performing a manipulation of the argument path results in path traversal. It is possible to initiate the attack remotely. The exploit is now public and may be used. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 08/27/2026
The bsmi021 mcp-file-context-server version 1.0.0 contains a critical path traversal vulnerability within its Path Resolution component, specifically located in the read_context function found in src/index.ts. This flaw arises from insufficient validation of user-supplied input passed as the path argument. When an attacker provides a manipulated path string containing directory traversal sequences such as dot-dot-slash or encoded variations thereof, the application fails to properly sanitize these inputs before processing them against the file system. Consequently, this allows for unauthorized access to files and directories that reside outside the intended root context of the server. The vulnerability represents a classic instance of improper input validation where the software does not adequately restrict the scope of accessible resources based on user-provided data.
From a technical perspective, this issue aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory. By leveraging path traversal techniques, an attacker can navigate up the directory hierarchy using relative paths or absolute path manipulation depending on how the underlying operating system resolves the input. Since the read_context function is responsible for retrieving file context data, successfully exploiting this vulnerability could allow an adversary to read sensitive configuration files, source code, environment variables containing secrets, or other critical system resources that are not meant to be exposed through this API endpoint. The lack of robust canonicalization checks means that even if some basic filtering exists, sophisticated encoding techniques can often bypass these naive defenses.
The operational impact of this vulnerability is severe due to its remote exploitability and the current availability of public exploits. Because the attack vector is network-based, a threat actor does not need local access or authentication credentials to initiate the exploitation process, provided they have connectivity to the service port exposed by bsmi021 mcp-file-context-server. The existence of publicly available proof-of-concept code significantly lowers the barrier for entry, enabling less sophisticated attackers to compromise systems running this specific version. This increases the likelihood of automated scanning and opportunistic attacks targeting vulnerable instances across the internet. Successful exploitation could lead to a complete breach of confidentiality regarding stored data and potentially serve as an initial foothold for further lateral movement within a network if sensitive credentials or internal architecture details are exposed through file contents.
In terms of threat modeling, this vulnerability maps directly to MITRE ATT&CK technique T1083: File and Directory Discovery, which describes adversaries searching local systems for information before exfiltration. Furthermore, it facilitates the broader category of Path Traversal often associated with initial access or data staging phases in an attack chain. The fact that the project maintainers have been notified via issue reports but have not yet responded highlights a critical gap in supply chain security and vendor responsiveness. Organizations relying on this component are currently exposed to unpatched risks without official mitigation guidance from the developers, necessitating immediate defensive actions independent of upstream fixes.
To mitigate this risk, organizations should immediately isolate or disable the bsmi021 mcp-file-context-server service if it is not strictly required for business operations. If the service must remain active, implementing a reverse proxy with strict input filtering rules can help block known path traversal patterns before they reach the application layer. Additionally, deploying Web Application Firewalls configured to detect and reject requests containing directory traversal sequences provides an additional layer of defense. It is also advisable to enforce least-privilege principles by running the server process under a restricted user account that lacks permissions to access sensitive system directories or configuration files outside its designated working tree. Until the vendor releases a patched version, continuous monitoring for exploitation attempts and regular audits of file access logs are recommended to detect any unauthorized read operations indicative of successful traversal attacks.