Software Engineering Institute

Overview

A log-injection vulnerability in the LibreChat RAG API, version 0.7.0, is caused by improper sanitization of user-supplied input written to system logs. An authenticated attacker can forge or manipulate log entries by inserting CRLF characters, compromising the integrity of audit records. This flaw may further enable downstream attacks if the tampered logs are processed or displayed by insecure log-management tools.

Description

LibreChat’s retrieval-augmented generation (RAG) application programming interface (API) is a specialized, asynchronous backend service developed with Python FastAPI and LangChain that facilitates document-based RAG through a file-level, ID-based indexing system. It operates by extracting and chunking text from user-uploaded files, generating high-dimensional embeddings via providers like OpenAI or local Ollama instances, and storing them in a PostgreSQL database equipped with the pgvector extension for efficient semantic search.

A log-injection vulnerability occurs when an application fails to properly sanitize or validate untrusted user input before including it in system log files, allowing an attacker to manipulate the integrity of the audit trail. By inserting line-feed or carriage-return (CRLF) characters in a POST request, specifically in the file_id parameter of the form data, an authenticated attacker can forge fake log entries.

Impact

By exploiting this vulnerability, an authenticated attacker can obfuscate malicious activity, misdirect forensic investigations, or impersonate other users. Furthermore, if the logs are later viewed through a web-based administrative console or an unsecure log-management tool, this vulnerability can escalate into secondary attacks such as cross-site scripting (XSS) or remote command execution.

Solution

Unfortunately, we were unable to reach the vendor to coordinate this vulnerability. Since a patch is unavailable, we can only offer mitigation strategies. The following workarounds can help mitigate this vulnerability's impact on the targeted environment:

• Sanitize input logs with a filter in the RAG ingest to prevent malicious data.
• Disable the pgvector extension in PostgreSQL, if not in use.
• Validate RAG output before passing it to other tools to prevent relaying of data that could lead to indirect prompt injection.

These recommendations are not mutually exclusive and can be implemented in combination to provide layered protection. By taking these steps, organizations can reduce their risk exposure until the vendor addresses the underlying vulnerabilities.

Acknowledgements

Thanks to Caio Bittencourt for coordinating the disclosure of this vulnerability. This document was written by Dr. Elke Drennan, CISSP.

Vendor Information