The vulnerability, identified as 'Artifact Pin Decay', lies in the vLLM library's failure to consistently propagate revision pinning across all artifact loading paths. When an operator specifies a model or code revision using --revision or --code-revision, the expectation is that all associated artifacts—such as model weights, configurations, and processors—are loaded from that specific revision. However, the analysis of the provided patches reveals that this was not the case in several parts of the codebase.
The root cause of the vulnerability is the omission of the revision or code_revision parameter in various function calls responsible for downloading or loading model artifacts. This oversight leads to a situation where, despite a pinned deployment, vLLM could fetch and use artifacts from the default branch of a repository. This breaks the operational guarantee of a pinned deployment, making it difficult to ensure reproducibility, conduct security reviews, and perform reliable audits.
The identified vulnerable functions are all related to the loading of models and their components. For instance, gguf_loader._prepare_weights downloaded GGUF files without a revision, KimiAudioForCausalLM.__init__ and KimiAudioModel.__init__ loaded configurations and weights for the Kimi-Audio model from unpinned revisions, and BgeM3EmbeddingModel.__init__ did the same for secondary weights. Similarly, KimiK25ImageProcessor.__init__ loaded an image processor from the default revision, and registry._try_resolve_transformers failed to enforce the code_revision pin when loading dynamic model classes.
The patches address these issues by ensuring that the revision and code_revision from the model configuration are passed down to all relevant function calls. This ensures that all artifacts are loaded from the intended, pinned revision, thereby restoring the integrity of the deployment.