arXiv:2605.15152cs.LGcs.AI2026-05

通过注入异常值,让大模型量化后触发恶意行为。

Widening the Gap: Exploiting LLM Quantization via Outlier Injection

论文配图:Widening the Gap: Exploiting LLM Quantization via Outlier Injection
图 1 · 摘自论文原文
  • 利用量化中异常值导致权重归零的特性,注入恶意异常值。
  • 在多种先进量化方法(如AWQ、GPTQ)下成功诱导恶意行为,成功率高。
  • 揭示了主流量化方案的潜在安全风险,适合关注AI安全的研究者。

大模型量化已成为内存高效部署的关键技术。近期研究发现,量化方案可能带来严重安全风险:攻击者可发布看似无害的全精度模型,但在用户量化后触发恶意行为。然而,现有量化条件攻击仅针对较简单的量化方法,因攻击者需预估量化下保持不变的权重区域,难以适用于更流行、更复杂的方案,限制了实际影响。本文首次提出一种可广泛触发恶意行为的量化条件攻击,适用于包括AWQ、GPTQ和GGUF I-quants在内的多种先进量化方法。该攻击利用现代量化方法共有的一个简单特性:大异常值会导致其他权重被舍入为零。通过向特定权重块注入异常值,攻击者可引发可预测的权重坍塌。由此可构造出外观正常的全精度模型,在量化后表现出多种恶意行为。我们在三种攻击场景和多个LLM上进行充分评估,结果表明该攻击在先前攻击失效的多种量化方法上均取得高成功率。首次证明,量化安全风险不仅存在于简单方案,也广泛存在于复杂且广泛应用的量化方法中。

原文摘要 · Abstract (English)

LLM quantization has become essential for memory-efficient deployment. Recent work has shown that quantization schemes can pose critical security risks: an adversary may release a model that appears benign in full precision but exhibits malicious behavior once quantized by users. However, existing quantization-conditioned attacks have been limited to relatively simple quantization methods, where the attacker can estimate weight regions that remain invariant under the target quantization. Notably, prior attacks have consistently failed to compromise more popular and sophisticated schemes, limiting their practical impact. In this work, we introduce the first quantization-conditioned attack that consistently induces malicious behavior that can be triggered by a broad range of advanced quantization techniques, including AWQ, GPTQ, and GGUF I-quants. Our attack exploits a simple property shared by many modern quantization methods: large outliers can cause other weights to be rounded to zero. Consequently, by injecting outliers into specific weight blocks, an adversary can induce a targeted, predictable weight collapse in the model. This effect can be used to craft seemingly benign full-precision models that exhibit a wide range of malicious behaviors after quantization. Through extensive evaluation across three attack scenarios and LLMs, we show that our attack achieves high success rates against a broad range of quantization methods on which prior attacks fail. Our results demonstrate, for the first time, that the security risks of quantization are not restricted to simpler schemes but are broadly relevant across complex, widely-used quantization methods.

大模型安全量化攻击异常值注入

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