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Route to Rome Attack: Directing LLM Routers to Expensive Models via Adversarial Suffix Optimization

3 Pith papers cite this work. Polarity classification is still indexing.

3 Pith papers citing it
abstract

Cost-aware routing dynamically dispatches user queries to models of varying capability to balance performance and inference cost. However, the routing strategy introduces a new security concern that adversaries may manipulate the router to consistently select expensive high-capability models. Existing routing attacks depend on either white-box access or heuristic prompts, rendering them ineffective in real-world black-box scenarios. In this work, we propose R$^2$A, which aims to mislead black-box LLM routers to expensive models via adversarial suffix optimization. Specifically, R$^2$A deploys a hybrid ensemble surrogate router to mimic the black-box router. A suffix optimization algorithm is further adapted for the ensemble-based surrogate. Extensive experiments on multiple open-source and commercial routing systems demonstrate that {R$^2$A} significantly increases the routing rate to expensive models on queries of different distributions. Code and examples: https://github.com/thcxiker/R2A-Attack.

fields

cs.CR 2 cs.CL 1

years

2026 3

verdicts

UNVERDICTED 3

representative citing papers

HyDRA: Hybrid Dynamic Routing Architecture for Heterogeneous LLM Pools

cs.CL · 2026-05-16 · unverdicted · novelty 6.0

HyDRA routes queries to cost-effective LLMs by predicting multi-dimensional capability requirements with a multi-head encoder and applying shortfall matching against configuration-defined model profiles, delivering up to 72.5 percent cost savings on coding benchmarks while remaining decoupled from具体

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