Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer LLMs

Jiakun Li, Guowei Song, Sijia Li, Xingwei He, Hongzheng Chai, Yuan Yuan


Abstract
Preserving safety alignment during large language models fine-tuning is critical, however, recent studies have demonstrated that even benign fine-tuning data may contain safety-degrading samples that silently undermine such alignment. Existing approaches typically identify safety-degrading samples using representations from a single safety-sensitive layer. However, whether a single safety-sensitive layer is sufficient for identifying such samples in multilingual settings remains unclear, where representation patterns may vary across languages. Our cross-lingual analysis shows that sensitive layers are only partially shared across languages and that safety-relevant signals often span multiple layers. Motivated by these observations, we propose MMSafe, a multi-layer framework for multilingual safety-degrading data identification that jointly leverages shared and language-specific sensitive layers. Extensive experiments across multiple models, languages, and safety benchmarks demonstrate that MMSafe reduces the average harmful-response ratio by 60% compared with random filtering and outperforms the strongest single-layer baseline, demonstrating the effectiveness of multi-layer modeling for robust multilingual safety alignment. Code is available at https://anonymous.4open.science/r/MMSAFE.
Anthology ID:
2026.emnlp-main.1492
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
34105–34120
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1492/
DOI:
Bibkey:
Cite (ACL):
Jiakun Li, Guowei Song, Sijia Li, Xingwei He, Hongzheng Chai, and Yuan Yuan. 2026. Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer LLMs. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 34105–34120, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer LLMs (Li et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1492.pdf