CVE-2026-26013: LangChain affected by SSRF via image_url token counting in ChatOpenAI.get_num_tokens_from_messages

Server-Side Request Forgery (SSRF) in ChatOpenAI Image Token Counting

Summary The ChatOpenAI.getnumtokensfrommessages() method fetches arbitrary imageurl values without validation when computing token counts for vision-enabled models. This allows attackers to trigger Server-Side Request Forgery (SSRF) attacks by providing malicious image URLs in user input.

Severity Low - The vulnerability allows SSRF attacks but has limited impact due to: - Responses are not returned to the attacker (blind SSRF) - Default 5-second timeout limits resource exhaustion - Non-image responses fail at PIL image parsing

Impact An attacker who can control image URLs passed to getnumtokensfrommessages() can: - Trigger HTTP requests from the application server to arbitrary internal or external URLs - Cause the server to access internal network resources (private IPs, cloud metadata endpoints) - Cause minor resource consumption through image downloads (bounded by timeout)

Note: This vulnerability occurs during token counting, which may happen outside of model invocation (e.g., in logging, metrics, or token budgeting flows).

Details The vulnerable code path: 1. getnumtokensfrommessages() processes messages containing imageurl content blocks 2. For images without detail: "low", it calls urltosize() to fetch the image and compute token counts 3. urltosize() performs httpx.get(imagesource) on any URL without validation 4. Prior to the patch, there was no SSRF protection, size limits, or explicit timeout

File: libs/partners/openai/langchainopenai/chatmodels/base.py

Patches The vulnerability has been patched in langchain-openai==1.1.9 (requires langchain-core==1.2.11).

The patch adds: 1. SSRF validation using langchaincore.security.ssrfprotection.validatesafeurl() to block: - Private IP ranges (RFC 1918, loopback, link-local) - Cloud metadata endpoints (169.254.169.254, etc.) - Invalid URL schemes 2. Explicit size limits (50 MB maximum, matching OpenAI's payload limit) 3. Explicit timeout (5 seconds, same as httpx.get default) 4. Allow disabling image fetching via allowfetchingimages=False parameter

Workarounds If you cannot upgrade immediately:

1. Sanitize input: Validate and filter imageurl values before passing messages to token counting or model invocation 2. Use network controls: Implement egress filtering to prevent outbound requests to private IPs