Diagnosing and Repairing Unsafe Channels in Vision-Language Models via Causal Discovery and Dual-Modal Safety Subspace Projection

TL;DR

This paper introduces CARE, a framework that diagnoses unsafe channels in vision-language models using causal analysis and repairs them with safety subspace projection, improving safety robustness without harming performance.

Contribution

The work presents a novel causal analysis and dual-modal safety subspace projection method for diagnosing and repairing unsafe behaviors in LVLMs.

Findings

Significantly improves safety robustness on multiple benchmarks.

Effectively suppresses unsafe features while maintaining semantic accuracy.

Demonstrates good transferability against unseen attacks.

Abstract

Large Vision-Language Models (LVLMs) have achieved impressive performance across multimodal understanding and reasoning tasks, yet their internal safety mechanisms remain opaque and poorly controlled. In this work, we present a comprehensive framework for diagnosing and repairing unsafe channels within LVLMs (CARE). We first perform causal mediation analysis to identify neurons and layers that are causally responsible for unsafe behaviors. Based on these findings, we introduce a dual-modal safety subspace projection method that learns generalized safety subspaces for both visual and textual modalities through generalized eigen-decomposition between benign and malicious activations. During inference, activations are dynamically projected toward these safety subspaces via a hybrid fusion mechanism that adaptively balances visual and textual corrections, effectively suppressing unsafe features while preserving semantic fidelity. Extensive experiments on multiple safety benchmarks demonstrate that our causal-subspace repair framework significantly enhances safety robustness without degrading general multimodal capabilities, outperforming prior activation steering and alignment-based baselines. Additionally, our method exhibits good transferability, defending against unseen attacks.