CVE-2026-89039

A caller who can invoke the convert_playwright_script prompt in mcp-k6 can pass a bare file path as the playwright_script argument and receive the contents of any file readable by the user running the server, including SSH keys and cloud credentials in that user's home directory (path traversal). The working-directory restriction applied to '@'-prefixed paths can also be bypassed with a symbolic link inside the working directory that points outside it.

A caller who can invoke the convert_playwright_script prompt in mcp-k6 can pass a bare file path as the playwright_script argument and receive the contents of any file readable by the user running the server, including SSH keys and cloud credentials in that user's home directory (path traversal). The working-directory restriction applied to '@'-prefixed paths can also be bypassed with a symbolic link inside the working directory that points outside it.

The convert_playwright_script prompt in the k6 MCP server accepts a file path as its playwright_script argument. Paths given in the documented '@'-prefixed form are restricted to the server's current working directory, but a bare path is resolved by a separate undocumented code path that applies no such restriction. A caller able to invoke the prompt can therefore read any file readable by the user running the server, including files outside the working directory, and receives the file contents in the prompt response. A leading '~' is expanded to the user's home directory, so credential files such as SSH private keys are directly addressable. The working-directory restriction is additionally bypassable through a symbolic link inside the working directory that points outside it, because the path is not canonicalized before the restriction is applied. All releases from v0.3.0 onward are affected; releases v0.3.0 and v0.4.0 apply no restriction to either form.

A caller who can invoke the convert_playwright_script prompt in mcp-k6 can pass a bare file path as the playwright_script argument and receive the contents of any file readable by the user running the server, including SSH keys and cloud credentials in that user's home directory (path traversal). The working-directory restriction applied to '@'-prefixed paths can also be bypassed with a symbolic link inside the working directory that points outside it.