Unsafe by Reciprocity: How Generation-Understanding Coupling Undermines Safety in Unified Multimodal Models
For developers and users of unified multimodal models, this paper identifies a fundamental safety weakness arising from cross-functionality coupling, highlighting the need for holistic safety evaluation beyond isolated analyses.
This work reveals that the tight integration of understanding and generation in Unified Multimodal Models (UMMs) creates structural safety vulnerabilities, proposing a novel attack paradigm (RICE) that exploits bidirectional interactions. Experiments show high Attack Success Rates (ASR) in both Generation-to-Understanding and Understanding-to-Generation pathways, demonstrating previously overlooked safety risks.
Recent advances in Large Language Models (LLMs) and Text-to-Image (T2I) models have led to the emergence of Unified Multimodal Models (UMMs), where multimodal understanding and image generation are tightly integrated within a shared architecture. Prior studies suggest that such reciprocity enhances cross-functionality performance through shared representations and joint optimization. However, the safety implications of this tight coupling remain largely unexplored, as existing safety research predominantly analyzes understanding and generation functionalities in isolation. In this work, we investigate whether cross-functionality reciprocity itself constitutes a structural source of vulnerability in UMMs. We propose RICE: Reciprocal Interaction-based Cross-functionality Exploitation, a novel attack paradigm that explicitly exploits bidirectional interactions between understanding and generation. Using this framework, we systematically evaluate Generation-to-Understanding (G-U) and Understanding-to-Generation (U-G) attack pathways, demonstrating that unsafe intermediate signals can propagate across modalities and amplify safety risks. Extensive experiments show high Attack Success Rates (ASR) in both directions, revealing previously overlooked safety weaknesses inherent to UMMs.