Langfuse Webhook Component Server-Side Request Forgery Vulnerability

A server-side request forgery (SSRF) vulnerability has been identified in Langfuse versions through 3.88.0. The issue arises in the Webhook Handler component, specifically within the 'promptChangeEventSourcing' function of 'web/src/features/prompts/server/routers/promptRouter.ts'. This vulnerability allows remote attackers to manipulate user-controlled URI parameters, potentially probing and exploiting internal services of the target system.

Impact

Exploitation of this vulnerability allows attackers to access internal IP addresses and services, effectively using the vulnerable server as a proxy to attack internal infrastructure. This could involve scanning for internal services, reading sensitive files, extracting cloud metadata with credentials, or pivoting to other internal systems.

Reproduction

To reproduce this vulnerability, create a webhook in a Langfuse project, selecting 'prompt' as the event source. Enter an internal IP address or domain as the webhook URL and leave the event action as default. After the webhook is created, trigger it by creating a prompt, which will activate the webhook and exploit the SSRF vulnerability by sending a request to the specified internal URL.