GHSA-vf9j-h32g-2764: mcp-package-docs vulnerable to command injection in several tools
SummaryA command injection vulnerability exists in the `mcp-package-docs` MCP Server. The vulnerability is caused by the unsanitized use of input parameters within a call to `child_process.exec`, enabling an attacker to inject arbitrary system commands. Successful exploitation can lead to remote code execution under the server process's privileges.The server constructs and executes shell commands using unvalidated user input directly within command-line strings. This introduces the possibility of shell metacharacter injection (`|`, `>`, `&&`, etc.).DetailsThe MCP Server exposes tools to access documentation for several types of packages.  An MCP Client can be instructed to execute additional actions for example via prompt injection when asked to read package documentation. Below some example of vulnerable code and different ways to test this vulnerability including a real example of indirect prompt injection that can lead to arbitrary command injection.Vulnerable codeThe following snippet illustrates the vulnerable code pattern used in the MCP Server’s tooling. **Note**: These is only one instance, but similar patterns may exist elsewhere in the codebase.Realistic Example - Indirect prompt injection via package docsCreate a local go package under home folder (in my setup is `/home/ubuntu/`)I created a local package to simplify the PoC.Add prompt instructions in the comment of `mypackage/mypackage.go`check the docVerify the file `/tmp/TEST`1 does **not** exist (on the host machine):setup your client IDEopen the chat and enter the following prompt (it's an example - replace `/home/[USER]/` with the correct home folder)run the `describe_go_package` tool. The request will look like the following:Observe that the response will contain the doc content but will also trigger the `describe_go_package` tool execution (again) with a malicious payload that can lead to command injection on the host machinerun the `describe_go_package` tool (if you have auto run functionality enabled this will be executed without user interaction)Result:Confirm that the injected command executed:Using MCP InspectorOpen the MCP Inspector:In MCP Inspector:set transport type: `STDIO`set the `command` to `npx`set the arguments to `mcp-package-docs`click Connectgo to the **Tools** tab and click **List Tools**select the `describe_go_package` toolVerify the file `/tmp/TEST` does **not** exist:In the **package** field, input:Click **Run Tool**Observe the request being sent:Response:Confirm that the injected command executed:RemediationTo mitigate this vulnerability, I suggest to avoid using `child_process.exec` with untrusted input. Instead, use a safer API such as [`child_process.execFile`](https://nodejs.org/api/child_process.html#child_processexecfilefile-args-options-callback), which allows you to pass arguments as a separate array — avoiding shell interpretation entirely.ImpactCommand Injection / Remote Code Execution (RCE)Referenceshttps://equixly.com/blog/2025/03/29/mcp-server-new-security-nightmare/https://invariantlabs.ai/blog/mcp-github-vulnerabilitySimilar Issueshttps://github.com/advisories/GHSA-gjv4-ghm7-q58qhttps://github.com/advisories/GHSA-5w57-2ccq-8w95https://github.com/advisories/GHSA-3q26-f695-pp76Response TimelineReceived report of security finding 8:19AM (Melbourne/Australia)Reviewed report and responded to researcher by 8:47AM requesting vulnerability detailsReceived detailed report at 9:33AMInvestigated and issued a fix at 10:35AM with updated release (v0.1.27, then v0.1.28) shortly after.Patched in https://github.com/sammcj/mcp-package-docs/releases/tag/v0.1.28As this repo is no longer in active development the package was marked as deprecated on npm and the GitHub repository archived (re-opened to update this report)
CVSS v3.1: 7.5