A Survey of Secure Retrieval-Augmented Generation

Yuming XU, Mingtao Zhang, Zhuohan Ge, Haoyang LI, Nicole HU, Yongqi Zhang, Zhiyuan Wen, Chen Jason Zhang, Li Qing, Lei Chen


Abstract
Retrieval-augmented generation (RAG) improves large language models (LLMs) with external knowledge, but this access path creates security risks distinct from inherent prompt-only or parametric-model flaws. We frame secure RAG as securing external knowledge access. We conducted a systematic search and curated 135 works on attacks, defenses, and security evaluation, and organized them with SLOT: a taxonomy along the attack Surface (S) and the corresponding defense Layer (L), with cross-cutting axes Objective (O) and attack-target scope (T). Mapping these studies onto an external knowledge-access pipeline, we expose three mismatches: target mismatch (T2 attacks outpace T2 defenses and evaluation), stage mismatch (S1 attacks outnumber L1 defenses), and signal mismatch (fluent, retrievable, corpus-fitting S1 attacks challenge anomaly-based L2/L3 defenses). Finally, we discuss directions for more realistic targets, surface-complete defense stacks, standardized evaluation, confidentiality, and multimodal and agentic systems, and release the screening process, selected-paper metadata, and machine-readable SLOT labels at https://github.com/TreeAI-Lab/Awesome-RAG-Security.
Anthology ID:
2026.findings-emnlp.241
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
5072–5095
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.241/
DOI:
Bibkey:
Cite (ACL):
Yuming XU, Mingtao Zhang, Zhuohan Ge, Haoyang LI, Nicole HU, Yongqi Zhang, Zhiyuan Wen, Chen Jason Zhang, Li Qing, and Lei Chen. 2026. A Survey of Secure Retrieval-Augmented Generation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 5072–5095, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
A Survey of Secure Retrieval-Augmented Generation (XU et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.241.pdf