Text-Anchored Semantic Perturbations for Transferable Jailbreak Attacks on Multimodal Large Language Models

Wenyun Li, Guiping Cao, Xiangyuan Lan, Zheng Zhang


Abstract
Multimodal Large Language Models (MLLMs) have achieved remarkable progress in vision-language interaction, yet their safety alignment remains vulnerable to jailbreak attacks. A key challenge is that safety behavior learned in the textual space does not reliably transfer to fused cross-modal representations, leaving multimodal inputs exploitable through latent semantic cues. We propose __Text-Anchored Semantic Perturbation Attack__ (TA-SPA), a black-box jailbreak framework that optimizes transferable perturbations in a text-anchored semantic space. TA-SPA integrates __Text-Anchored Semantic Factorization__ (TASF), which disentangles cross-modal semantic factors from modality-specific residuals, with __Semantic-Preserving Augmentation__ (SPA), which diversifies harmful target anchors while preserving semantic consistency. Extensive experiments show that TA-SPA consistently outperforms prior jailbreak attacks, transfers to commercial MLLMs, and remains effective under representative defenses, underscoring the need for representation-level safety alignment beyond input-level filtering.
Anthology ID:
2026.findings-emnlp.165
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
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SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3500–3515
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URL:
https://aclanthology.org/2026.findings-emnlp.165/
DOI:
Bibkey:
Cite (ACL):
Wenyun Li, Guiping Cao, Xiangyuan Lan, and Zheng Zhang. 2026. Text-Anchored Semantic Perturbations for Transferable Jailbreak Attacks on Multimodal Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 3500–3515, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Text-Anchored Semantic Perturbations for Transferable Jailbreak Attacks on Multimodal Large Language Models (Li et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.165.pdf