DisarmRAG: Stealthy Retriever-Centric Poisoning to Disable Self-Correction in Retrieval-Augmented Generation (Extended Version)

Retrieval-Augmented Generation (RAG) has become a standard approach for improving the reliability of large language models (LLMs). Prior work demonstrates the vulnerability of RAG systems by misleading them into generating attacker-chosen outputs through poisoning the knowledge base. However, we observe that the effectiveness of these attacks is substantially undermined in the real-world deployment, where LLMs exhibit a strong self-correction ability (SCA). This ability is typically triggered by the mainstream configuration of LLMs, indicating a substantial gap between idealized research settings and practical scenarios. To address this issue, we systematically reflect on the limitations of prior RAG attacks and introduce DisarmRAG, a novel poisoning paradigm that focuses on the retriever, instead of the conventional approach of only poisoning the knowledge base. By compromising the retriever, our method can inject arbitrary anti-SCA instructions into the context provided to LLMs, effectively suppressing the SCA and enforcing attacker-chosen outputs. In particular, we craft a novel and systematic attack framework consisting of 1) an iterative co-optimization process to ensure the effectiveness of the anti-SCA instructions and 2) a stealthy model editing technique based on contrastive learning to facilitate the delivery of the attack payload. We extensively evaluate DisarmRAG across six LLMs and three QA benchmarks, and the results, with success rates exceeding 90%, confirm its efficacy. We additionally validate the effectiveness of our attack under various detection defenses, highlighting stealthiness, which is another critical aspect to consider in real-world attacks.