Affected: vllm-project vllm

vLLM is an inference and serving engine for large language models (LLMs). From 0.6.1 to before 0.20.0, there is a a Token Injection vulnerability in vLLM’s multimodal processing. Unauthenticated, text-only prompts that spell special tokens are interpreted as control. Image and video placeholder sequences supplied without matching data cause vLLM to index into empty grids during input-position computation, raising an unhandled IndexError and terminating the worker or degrading availability. Multimodal paths that rely on image_grid_thw/video_grid_thw are affected. This vulnerability is fixed in 0.20.0.

Affected: PyPI: vllm

## Summary This report explains a Token Injection vulnerability in vLLM’s multimodal processing. Unauthenticated, text-only prompts that spell special tokens are interpreted as control. Image and video placeholder sequences supplied without matching data cause vLLM to index into empty grids during input-position computation, raising an unhandled IndexError and terminating the worker or degrading availability. Multimodal paths that rely on `image_grid_thw`/`video_grid_thw` are affected. Severity: High (remote DoS). Reproduced on vLLM 0.10.0 with Qwen2.5-VL.

## Details - Affected component: multimodal input position computation. - File/functions (paths are indicative): - vllm/model_executor/layers/rotary_embedding.py - get_input_positions_tensor(...) - _vl_get_input_positions_tensor(...) - Failure mechanism: - The code counts detected vision tokens and then indexes video_grid_thw/image_grid_thw accordingly. - When user input carries placeholder tokens but no actual multimodal payload, these grids are empty. The code does not bounds-check before indexing.

Representative snippet (context): ```python # vllm/model_executor/layers/rotary_embedding.py @classmethod def _vl_get_input_positions_tensor( cls, input_tokens, hf_config, image_grid_thw, video_grid_thw, ..., ): # detect video tokens video_nums = (vision_tokens == video_token_id).sum() # later in processing t, h, w = ( video_grid_thw[video_index][0], # IndexError…