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arXiv · 2608.15913

Conjunctive Poisoning in AI Supply-Chain Applications

Nokimul Hasan Arif·Qian Lou·Mengxin Zheng
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Abstract

Large Language and Vision-Language Models are increasingly deployed through inference pipelines that include prompt wrappers (e.g., templates and post-processing scripts) and configuration metadata (e.g., JSON/YAML files) that together shape model outputs. While model weights and binaries are routinely verified, these textual deployment artifacts remain weakly protected despite directly influencing runtime behavior. We show that a malicious developer can pair a benign-looking wrapper with crafted metadata to deterministically alter post-generation behavior without modifying model weights, training data, or inference backend. We study this behavior through a controlled conjunctive-gate implementation, where activation depends on both an embedded wrapper marker and cryptographically bound metadata. We evaluate the attack across fifteen open- and closed-source LLM/VLM deployments, and assess prompt and system level defenses including static metadata inspection, wrapper scanners, PromptShield, and SigStore-based artifact signing. To mitigate this risk, we introduce TIF-BAH, a lightweight middleware defense that verifies wrapper integrity and records behavioral attestations during inference. Our results reveal that wrapper-metadata interactions form an under-protected execution layer in modern AI deployments, exposing a deployment-time behavioral risk that is not captured by model-weight or prompt-level defenses. Code is available at https://github.com/N-H-Arif/llm_temp.

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Nokimul Hasan Arif, Qian Lou, Mengxin Zheng. 2026-08-16. Conjunctive Poisoning in AI Supply-Chain Applications. https://arxiv.org/abs/2608.15913

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