T03 · Remote Payload Retrieval and Execution
Error
- Location
- SKILL.md:49
- Finding
- Unverified Remote Homebrew Installer Is Downloaded and Executed## Vulnerability Details **File Location**: `SKILL.md`, line 49 **Vulnerability Type**: Remote payload retrieval and execution **Risk Level**: High ### Vulnerable Code ```bash /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" ``` ### Technical Analysis The deployment template downloads a shell script from the mutable `HEAD` branch of an external GitHub repository and immediately executes the response with Bash. Although the URL belongs to the official Homebrew repository, the command does not pin the installer to an immutable reviewed commit and does not validate a cryptographic checksum or signature. Consequently, the effective code executed during deployment can differ from the code reviewed during this audit. The operator has no opportunity to inspect the downloaded response before execution. Compromise of the upstream repository, a maintainer account, the delivery infrastructure, or the trusted TLS path could turn this installation command into arbitrary local code execution. This exceeds the minimum privilege and trust necessary to install Homebrew because safer alternatives can separate download, verification, review, and execution. ### Attack Path 1. An attacker compromises the upstream repository, a sufficiently privileged maintainer account, or another trusted component in the payload delivery path. 2. The attacker modifies the script served from `Homebrew/install/HEAD/install.sh`. 3. An operator follows the Layer 1 deployment instructions. 4. `curl` retrieves the modified script without commit pinning or integrity verification. 5. Command substitution passes the response directly to `/bin/bash`. 6. The attacker-controlled script executes with all permissions available to the deployment operator and may request or abuse elevated access during installation. ### Impact Assessment Successful exploitation provides arbitrary command execution under the invoking ac ...[truncated 475 chars]
- Remediation
- ## Remediation Suggestions 1. Do not pipe or interpolate network responses directly into a shell. 2. Pin the installer to a reviewed immutable release or full Git commit rather than `HEAD`. 3. Download the script to a protected local file first: ```bash curl --proto '=https' --tlsv1.2 --fail --show-error --location \ --output /tmp/homebrew-install.sh \ 'https://raw.githubusercontent.com/Homebrew/install/REVIEWED_COMMIT/install.sh' ``` 4. Verify the downloaded file against a trusted, vendor-published cryptographic checksum or signature before execution. 5. Inspect the downloaded script and execute it as a separate step only after verification. 6. Run installation with the least-privileged account possible and review every request for administrative authorization. 7. Prefer a trusted package-management or manually documented installation method when an independently verifiable installer artifact is unavailable. 8. Record the pinned version, checksum, verification result, and source URL in deployment logs to support reproducible audits.