CVE-2026-53923 — vLLM GGUF Kernels: int64_t to int truncation of tensor dimensions causes GPU buffer overflow

Affected: vllm-project vllm

vLLM is an inference and serving engine for large language models (LLMs). From 0.5.5 until 0.23.1rc0, integer truncation of tensor dimensions in vLLM's GGUF dequantize kernels (csrc/quantization/gguf/gguf_kernel.cu) causes partial tensor processing. The output tensor is allocated at full size via torch::empty (uninitialized memory), but the dequantize CUDA kernel processes only a truncated number of elements. The unfilled portion of the output tensor retains whatever was previously in GPU memory. In multi-tenant inference deployments, this residual GPU memory may contain tensor data from other users' inference requests, constituting information disclosure. This vulnerability is fixed in 0.23.1rc0.

GHSA-5jv2-g5wq-cmr4 — vLLM: GGUF dequantize kernel int truncation exposes uninitialized GPU memory in multi-tenant serving

Affected: PyPI: vllm

## Summary

Integer truncation of tensor dimensions in vLLM's GGUF dequantize kernels (`csrc/quantization/gguf/gguf_kernel.cu`) causes partial tensor processing. The output tensor is allocated at full size via `torch::empty` (uninitialized memory), but the dequantize CUDA kernel processes only a truncated number of elements. The unfilled portion of the output tensor retains whatever was previously in GPU memory. In multi-tenant inference deployments, this residual GPU memory may contain tensor data from other users' inference requests, constituting information disclosure.

## Root Cause

The `to_cuda_ggml_t` function pointer type at `ggml-common.h:1067` declares its element count parameter as `int` (32-bit):

```cpp using to_cuda_ggml_t = void (*)(const void * __restrict__ x, dst_t * __restrict__ y, int k, // 32-bit cudaStream_t stream); ```

All dequantize kernel functions (`dequantize_block_cuda`, `dequantize_row_q2_K_cuda`, etc. in `dequantize.cuh`) inherit this `int k` parameter and use it as the kernel launch grid size:

```cpp static void dequantize_block_cuda(..., const int k, cudaStream_t stream) { const int num_blocks = (k + 2*CUDA_DEQUANTIZE_BLOCK_SIZE - 1) / (2*CUDA_DEQUANTIZE_BLOCK_SIZE); dequantize_block<<<num_blocks, CUDA_DEQUANTIZE_BLOCK_SIZE, 0, stream>>>(vx, y, k); } ```

In `ggml_dequantize()` at `gguf_kernel.cu:85`, the caller passes `m * n`…

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CVE-2026-53923 — vLLM GGUF Kernels: int64_t to int truncation of tensor dimensions causes GPU buffer overflow

GHSA-5jv2-g5wq-cmr4 — vLLM: GGUF dequantize kernel int truncation exposes uninitialized GPU memory in multi-tenant serving