CVE-2026-55157

### Summary `token-optimizer-mcp` is vulnerable to OS command injection in the `smart_user` tool. The `get-user-info` operation accepts a user-controlled `username` argument and later interpolates it into a shell command executed through `execAsync()`: ```ts getent passwd "${username}" || grep "^${username}:" /etc/passwd ``` Although the value is wrapped in double quotes, POSIX shells still evaluate command substitution such as `$(...)` and backticks inside double quotes. As a result, an MCP client can provide a crafted username such as: ```text $(id > /tmp/TOKEN_OPTIMIZER_SMART_USER_ID) ``` and execute arbitrary local commands with the privileges of the user running the MCP server. This is a CWE-78 OS command injection issue. Tested version: ```text @ooples/token-optimizer-mcp v5.0.1 MCP serverInfo.name: token-optimizer-mcp MCP serverInfo.version: 0.2.0 ``` This issue is not related to the current `npm audit` dependency advisories. The vulnerability is in `token-optimizer-mcp`'s own tool implementation. --- ### Details The vulnerable code path is in the `smart_user` implementation. The `username` argument is eventually passed into a shell command similar to: ```ts const { stdout: passwdOut } = await execAsync( `getent passwd "${username}" || grep "^${username}:" /etc/passwd` ); ``` The problem is that `username` is controlled by the MCP tool caller and is inserted into a command string executed by a shell. Double quotes do not make this safe. In POSIX shells, command substitution is still evaluated inside double quotes: ```bash "$(id > /tmp/TOKEN_OPTIMIZER_SMART_USER_ID)" "`id`" ``` Therefore, a malicious `username` can execute arbitrary commands before `getent` or `grep` receives its arguments. The affected MCP tool call is: ```text tool: smart_user operation: get-user-info argument: username ``` Root cause: ```text MCP-controlled username → interpolated into shell command string → executed through execAsync() → shell evaluates $(...) / ba