T03 · Remote Payload Retrieval and Execution
Error
- Location
- USAGE.md:156
- Finding
- Remote Homebrew installer is piped directly into a shell<![CDATA[ ## Vulnerability Details **File Location**: `USAGE.md:156` **Vulnerability Type**: Remote mutable code execution without integrity verification **Risk Level**: High ### Vulnerable Code ```bash curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh | bash ``` ### Technical Analysis The installation guidance downloads a shell script from the current `HEAD` of a remote repository and immediately pipes it to Bash. The user cannot inspect the downloaded content before execution, and the command does not pin a commit, validate a checksum, or verify a cryptographic signature. Although the URL belongs to Homebrew's official GitHub repository, it is mutable. A compromise of the upstream repository, GitHub account, distribution infrastructure, DNS or TLS trust chain, or an unexpected upstream modification would change the code executed by users without requiring any change to this project. This behavior is not necessary for the Skill's core functionality. Homebrew is only suggested as part of troubleshooting the optional full-extraction method. ### Attack Path 1. An attacker compromises the referenced upstream repository, an authorized maintainer account, or another part of the download path. 2. The attacker modifies the script served from the `HEAD` URL. 3. A user follows the troubleshooting instructions and executes the documented command. 4. `curl` retrieves the attacker's current payload and streams it directly to Bash. 5. The payload executes with the privileges and environment of the invoking user. 6. If the installer or user subsequently invokes privileged operations, the compromise may extend to system-level changes. ### Impact Assessment Successful exploitation provides arbitrary command execution under the invoking user's account. The payload could read private user data, alter shell configuration, install persistence, steal credentials accessible to the user, or modify development tools and dependencies. The immediate ...[truncated 149 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions 1. Remove the direct `curl | bash` instruction. 2. Direct users to Homebrew's official installation documentation instead of executing remote content inline. 3. If an automated download is necessary: - Pin the installer to a reviewed release or immutable commit. - Download it to a local file. - Verify a documented cryptographic checksum or signature. - Allow the user to inspect the file before execution. - Execute it as a separate, explicit step. 4. Clearly state that Homebrew and Ruby are only required for the optional full-extraction method. 5. Avoid requesting administrator privileges unless a specific operation demonstrably requires them. ]]>