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Safety Fine-Tuning at (Almost) No Cost: A Baseline for Vision Large Language Models
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Shows that VLLM instruction fine-tuning erodes LLM safety and that harmful data in VL instruction sets contributes; releases VLGuard, a 2,000-image VL safety instruction dataset, and shows post-hoc or mixed fine-tuning with it greatly reduces attack success while keeping helpfulness.
Problem
Vision large language models are prone to generating harmful content and to simple jailbreaks, partly because vision-language instruction fine-tuning erodes the safety alignment inherited from the underlying LLM and training data contains harmful samples.
Approach
Curate VLGuard, a vision-language safety instruction-following dataset generated with GPT-4V covering harmful image and instruction categories, and use it either mixed into standard VLLM training or as a cheap post-hoc fine-tuning step paired with a small amount of helpfulness data.
Key results
- Post-hoc fine-tuning of LLaVA-v1.5-7B with VLGuard plus 5,000 LLaVA samples reduces VLGuard Safe-Unsafe ASR from 87.46% to 0.90% and Unsafe ASR from 72.62% to 0.23%, with helpfulness maintained.
- Mixed fine-tuning with VLGuard (about 0.3% of LLaVA stage-2 data) reduces FigStep ASR for LLaVA-v1.5-7B from 90.40% to 0.00% while raising the VLGuard Safe-Safe score from 18.82 to 20.78.
- Black-box TAP attack success on LLaVA-v1.5-7B drops from 62% to 20% (mixed) and 34% (post-hoc).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Fine-tune with VLGuard using post-hoc or mixed training | LLaVA-v1.5-7B · AdvBench Vanilla | ASR: 6.45 -> 0.00 | Helped |
| Fine-tune with VLGuard | LLaVA-v1.5-7B · FigStep | ASR: 90.40 -> 0.00 | Helped |
| Fine-tune with VLGuard | LLaVA-v1.5-13B · XSTest Safe | answer rate: 85.20 -> 77.20 | Hurt |
| Remove identified harmful training samples (ablation) | LLaVA-v1.5 · AdvBench Vanilla | ASR: 6.45 -> 5.77 | Helped |
| Use LoRA instead of full fine-tuning on the original, uncleaned data (ablation) | LLaVA-v1.5-7B · AdvBench Vanilla | ASR: 6.45 -> 10.62 | Hurt |
| Use only VLGuard safety data, without helpfulness examples (ablation) | LLaVA-v1.5-7B · XSTest Safe | answer rate: 91.20 -> 41.60 | Hurt |
| Add 5000 LLaVA helpfulness samples to VLGuard (ablation) | LLaVA-v1.5-7B · XSTest Safe | answer rate: 41.60 -> 80.80 | Helped |
| Add 5000 Alpaca text samples to VLGuard (ablation) | LLaVA-v1.5-7B · XSTest Safe | answer rate: 41.60 -> 81.10 | Helped |
| Use text-only Safety LLaMA data instead of multimodal VLGuard data (ablation) | LLaVA-v1.5-7B · VLGuard Safe-Unsafe | answer rate: 0.90 vs 85.13 | Hurt |
| Mix in VLGuard during training | LLaVA-v1.5-7B · TAP attack on AdvBench subset | attack success rate: 62.00 -> 20.00 | Helped |
| Fine-tune with VLGuard | MiniGPT-v2 · VLGuard Safe-Unsafe | answer rate: 88.17 -> 5.19 | Helped |
Surprising findings
- Fine-tuning on safety data alone causes exaggerated safety (XSTest safe answer rate drops to 41.6%), so helpfulness data must be mixed in.
- LoRA fine-tuning is less safe than full fine-tuning on identical data, and removing harmful LLaVA samples only partially restores safety.
Limitations
- Defense is not robust to sophisticated attacks; white-box adversarial attacks raise toxicity of fine-tuned models, though still below the original.
- Training set limited to 2,000 images due to GPT-4V cost.
- Llama-Guard has false negatives, so string matching is the primary metric.
Experimental setup
Datasets: VLGuard train LLaVA-v1.5 instruction data Alpaca Privacy Alert Hateful Memes Harmful Political Memes Harmful Object Dataset Bad Ads AdvBench XSTest FigStep MMLU
Benchmarks: AdvBench XSTest FigStep VLGuard MMLU AlpacaEval 2.0 ScienceQA VizWiz MMBench MM-Vet
Metrics: attack success rate win rate accuracy human win rate
Baselines: LLaVA-v1.5-7B LLaVA-v1.5-13B MiniGPT-v2 Safety LLaMA InstructBLIP Qwen-VL-Chat CogVLM InternLM-XComposer
Builds on: LLaVA-v1.5 MiniGPT-v2 FigStep Llama-Guard
Closest papers by meaning
- ETA: Evaluating Then Aligning Safety of Vision Language Models at Inference Time (ICLR 2025 · similarity 0.93)
- How Does Vision-Language Adaptation Impact the Safety of Vision Language Models? (ICLR 2025 · similarity 0.92)
- Cross-Modal Safety Mechanism Transfer in Large Vision-Language Models (ICLR 2025 · similarity 0.92)
- Do We Really Need Curated Malicious Data for Safety Alignment in Multi-modal Large Language Models? (CVPR 2025 · similarity 0.92)
- Fine-tuning Aligned Language Models Compromises Safety, Even When Users Do Not Intend To! (ICLR 2024 · similarity 0.91)
- Navigating the Safety Landscape: Measuring Risks in Finetuning Large Language Models (NeurIPS 2024 · similarity 0.91)
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