Description

Paperclip: Arbitrary File Read via Agent-Controlled adapterConfig.instructionsFilePath ### Summary Paperclip contains an arbitrary file read vulnerability that allows an attacker with an Agent API key to read files from the Paperclip server host filesystem. The vulnerability occurs because agents are allowed to modify their own adapterConfig through the /agents/:id API endpoint. The configuration field adapterConfig.instructionsFilePath is later read directly by the server runtime using fs.readFile(). Because no validation or path restriction is applied, an attacker can supply an arbitrary filesystem path. The Paperclip server then attempts to read that path from the host filesystem during agent execution. This breaks the intended trust boundary between agent runtime configuration and server host filesystem access, allowing a compromised or malicious agent to access sensitive files on the host system. ### Details #### Root Cause No path normalization, allowlist, or workspace boundary validation is applied before the filesystem read occurs. Agent configuration can be modified through the API endpoint: PATCH /api/agents/:id The validation schema allows arbitrary configuration fields inside adapterConfig. File: packages/shared/src/validators/agent.ts Schema fragment: adapterConfig: z.record(z.unknown()) Because of this schema, attackers can inject arbitrary configuration values, including: adapterConfig.instructionsFilePath During agent execution, the server runtime reads this path directly from the host filesystem using fs.readFile(). Relevant code path: packages/adapters/claude-local/src/server/execute.ts Execution flow: adapterConfig.instructionsFilePath ↓ execute() ↓ fs.readFile(instructionsFilePath) ↓ file content loaded into runtime Vulnerable logic: const instructionsContent = await fs.readFile(instructionsFilePath, "utf-8"); Because the value originates from attacker-controlled configuration and no validation or sandboxing is applied, this becomes a direct host filesystem read primitive. #### Affected Files Primary vulnerable file: packages/adapters/claude-local/src/server/execute.ts Relevant function: execute() Sensitive operation: fs.readFile(instructionsFilePath) Configuration source: PATCH /api/agents/:id Validation logic: packages/shared/src/validators/agent.ts #### Attacker Model Required privileges Attacker requires: Agent API key Agent credentials are intended for automation and integration with external runtimes. These credentials are commonly used by: agent runtime environments third-party integrations automation pipelines Agent credentials are not intended to grant direct access to the server host filesystem. No board or administrator privileges are required. #### Attacker Chain Complete exploit chain: Attacker obtains Agent API key ↓ PATCH /api/agents/:id ↓ Inject adapterConfig.instructionsFilePath ↓ POST /api/agents/:id/wakeup ↓ Server executes agent run ↓ execute.ts ↓ fs.readFile(attacker_path) ↓ Server reads host filesystem path This allows an attacker to read arbitrary files accessible to the Paperclip server process. #### Trust Boundary Violation Paperclip’s architecture assumes the following separation: Agent runtime ↓ Paperclip orchestration layer ↓ Server host filesystem Agents should only interact with repositories and workflows through the orchestration layer. However, because agent-controlled configuration is passed directly into fs.readFile, the boundary collapses: Agent configuration ↓ Server filesystem access This allows an agent to access files outside its intended permission scope. #### Why This Is a Vulnerability (Not Expected Behavior) The instructionsFilePath configuration appears intended for trusted operators configuring agent runtime behavior. However, the current API design allows agents themselves to modify this configuration through the agent API. Because agent credentials may be exposed to external systems or runtime environments, allowing them to control server filesystem paths introduces a security vulnerability. Therefore: Operator-controlled configuration → expected feature Agent-controlled configuration → arbitrary file read vulnerability The issue arises from insufficient separation between configuration authority and filesystem access authority. ### PoC The following PoC demonstrates that the server attempts to read an attacker-controlled filesystem path. To avoid accessing sensitive data, the PoC uses a non-existent path. #### Step 1 — Setup Environment Run server: $env:SHELL = "C:\Program Files\Git\bin\sh.exe" npx paperclipai onboard --yes Login Claude: claude /login #### Step 2 — Obtain Agent API key Create an agent via the UI or CLI and obtain its API key. Example: #### Step 3 — Identify agent ID GET /api/agents/me #### Step 4 — Inject malicious configuration PATCH /api/agents/{agentId} Payload example: powershell { "adapterConfig": { "instructionsFilePath": "C:\\definitely-does-not-exist-paperclip-poc.txt" } } Example PowerShell payload: powershell $patchBody = @{ adapterConfig = @{ instructionsFilePath = "C:\definitely-does-not-exist-paperclip-poc.txt" } } | ConvertTo-Json -Depth 10 Step 5 — Trigger execution POST /api/agents/{agentId}/wakeup #### Step 6 — Observe server log Server log shows: ENOENT: no such file or directory, open 'C:\definitely-does-not-exist-paperclip-poc.txt' at async Object.readFile at async Object.execute (.../adapter-claude-local/dist/server/execute.js) This confirms the server attempted to read an attacker-controlled filesystem path. ### Impact Successful exploitation allows attackers to read sensitive files accessible to the Paperclip server process. Examples of potentially exposed data include: environment configuration (.env) SSH private keys database credentials API tokens CI secrets Possible attacker actions: exfiltrate secrets access private repositories steal infrastructure credentials pivot into connected services Because Paperclip orchestrates repositories, agents, and automation tasks, disclosure of such secrets may lead to compromise of the broader deployment environment. ### Recommended Fix #### Restrict configuration authority Agents should not be allowed to modify filesystem-sensitive configuration fields. Example mitigation: adapterConfig.instructionsFilePath should only be configurable by board/admin actors. #### Path validation Restrict file access to a safe directory such as: workspace/ agent-config/ Reject: absolute paths system directories paths containing ".." #### Avoid direct filesystem reads from configuration Instead of: fs.readFile(user_supplied_path) use: readFile(workspaceSafePath) Example guard ts if ( request.auth?.principal === "agent" && body?.adapterConfig?.instructionsFilePath ) { throw new Error( "Agents are not permitted to configure instructionsFilePath" ); } ### Security Impact Statement An authenticated attacker with an Agent API key can modify their agent configuration to inject an arbitrary filesystem path into adapterConfig.instructionsFilePath. The Paperclip server reads this path during agent execution via fs.readFile, allowing the attacker to access files on the server host filesystem. ### Disclosure This vulnerability was discovered during security research on the Paperclip orchestration runtime and is reported privately to allow maintainers to patch the issue before public

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