T03 · Remote Payload Retrieval and Execution
Error
- Location
- SKILL.md:18
- Finding
- Unverified Remote Installer Executed Directly by Bash## Vulnerability Details **File Location**: `SKILL.md`, line 18 **Vulnerability Type**: Remote payload retrieval and execution **Risk Level**: High **Vulnerable Code**: ```bash bun --version || curl -fsSL https://bun.sh/install | bash ``` ### Technical Analysis If Bun is unavailable, this command downloads the current response from `https://bun.sh/install` and immediately executes it with Bash. The retrieved script is not pinned to a version and is not validated with a checksum or cryptographic signature before execution. HTTPS provides transport protection but does not guarantee that the endpoint, hosting infrastructure, DNS resolution, or upstream release process cannot be compromised. Because the downloaded content is never stored for inspection, the effective payload can change after the Skill has been reviewed. Installing Bun may be relevant to building the CLI, but direct execution of an unverified remote script is not the minimum-risk method necessary to provide the Skill's flight-information functionality. ### Attack Path 1. A user or agent follows the setup instructions on a system where `bun` is not installed. 2. The `bun --version` command fails, causing the shell to evaluate the command after `||`. 3. `curl` retrieves the current payload from `https://bun.sh/install`. 4. The response is passed directly to Bash without integrity or authenticity verification. 5. If the remote source or delivery chain has been compromised, attacker-controlled commands execute with the privileges of the invoking user. 6. Those commands can access user-readable data, alter files and shell configuration, install additional software, or retrieve and execute further payloads. ### Impact Assessment Successful exploitation provides arbitrary command execution under the account running the installation. The payload can read or modify any files available to that account, access environment variables and locally available credentia ...[truncated 297 chars]
- Remediation
- ## Remediation Suggestions - Remove the `curl | bash` installation pattern. - Prefer a trusted operating-system package manager or another installation channel that supports immutable versions and integrity verification. - Pin Bun to a specific reviewed version rather than installing the latest mutable release. - If a standalone installer is required, download it as a separate file, verify its published cryptographic checksum or signature, and present it for review before execution. - Require explicit user approval before installing runtime dependencies or modifying the environment. - Document the files and shell configuration that the installer is expected to modify. - Where practical, run the build in an isolated container or sandbox with no access to unrelated credentials or user files.