vLLM is an inference and serving engine for large language models. Prior to 0.26.0, the validation_exception_handler in vllm/entrypoints/openai/server_utils.py converts FastAPI RequestValidationError objects with str(exc), and sanitize_message in vllm/entrypoints/utils.py does not remove traceback-style file paths, allowing unauthenticated malformed JSON requests to /v1/chat/completions, /v1/completions, /tokenize, and /detokenize to disclose the OS username, home and virtual-environment paths, Python version, internal package structure, line numbers, and endpoint handler names. This issue is fixed in version 0.26.0.

Affected: PyPI: vllm

## Summary

When the vLLM API receives a malformed request (e.g., invalid JSON or missing required fields), FastAPI raises a Pydantic `RequestValidationError`. The `validation_exception_handler` in `vllm/entrypoints/openai/server_utils.py` converts this exception to a string via `str(exc)`, which includes the internal file path and line number of the handler function. The existing `sanitize_message()` function in `vllm/entrypoints/utils.py` strips memory addresses (e.g., `0x7f...`) but does not strip `File "...", line X` patterns. The result is a user-facing HTTP response that leaks internal system information.

## Impact

An unauthenticated attacker can extract the following with a single malformed request:

- **OS username** running the vLLM process (e.g., `ubuntu`) - **Home directory path** (e.g., `/home/ubuntu/`) - **Virtual environment path** (e.g., `vllm-env/`) - **Python version** (e.g., `3.12`) - **Internal package structure and line numbers** (e.g., `vllm/entrypoints/openai/chat_completion/api_router.py`) - **Handler function names per endpoint**, enabling precise version fingerprinting

This information aids attackers in constructing targeted exploits: environment paths narrow the attack surface, and handler function names + line numbers enable exact version identification even when the `/version` endpoint is disabled.

All POST endpoints that accept JSON bodies are affected, including `/v1/chat/completions`, `/v1/completions`, `/tokenize`, and `/detokenize`.

## W…

Affected: PyPI: vllm

## Summary

When the vLLM API receives a malformed request (e.g., invalid JSON or missing required fields), FastAPI raises a Pydantic `RequestValidationError`. The `validation_exception_handler` in `vllm/entrypoints/openai/server_utils.py` converts this exception to a string via `str(exc)`, which includes the internal file path and line number of the handler function. The existing `sanitize_message()` function in `vllm/entrypoints/utils.py` strips memory addresses (e.g., `0x7f...`) but does not strip `File "...", line X` patterns. The result is a user-facing HTTP response that leaks internal system information.

## Impact

An unauthenticated attacker can extract the following with a single malformed request:

- **OS username** running the vLLM process (e.g., `ubuntu`) - **Home directory path** (e.g., `/home/ubuntu/`) - **Virtual environment path** (e.g., `vllm-env/`) - **Python version** (e.g., `3.12`) - **Internal package structure and line numbers** (e.g., `vllm/entrypoints/openai/chat_completion/api_router.py`) - **Handler function names per endpoint**, enabling precise version fingerprinting

This information aids attackers in constructing targeted exploits: environment paths narrow the attack surface, and handler function names + line numbers enable exact version identification even when the `/version` endpoint is disabled.

All POST endpoints that accept JSON bodies are affected, including `/v1/chat/completions`, `/v1/completions`, `/tokenize`, and `/detokenize`.

## W…

Ein Angreifer kann mehrere Schwachstellen in vllm ausnutzen, um Informationen offenzulegen, Daten zu manipulieren, Sicherheitsmaßnahmen zu umgehen oder einen Denial-of-Service-Zustand herbeizuführen.