vLLM through 0.29.0 GPU KV Cache Leak via Mooncake Transfer ID Collision

Advisories

vLLM through 0.29.0 GPU KV Cache Leak via Mooncake Transfer ID Collision

severity: high
date: 9/21/2026
Affecting: vllm <= 0.29.0
CVE: CVE-2026-94627
CWE: CWE-401 Missing Release of Memory after Effective Lifetime
CVSS: 8.7
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References: Pull Request #49796
https://github.com/vllm-project/vllm/blob/v0.29.0/vllm/distributed/kv_transfer/kv_connector/v1/mooncake/mooncake_connector.py#L1978-L1989
https://github.com/vllm-project/vllm
Credit: Mingkai Yu, Jiapeng Li, Jiajia Liu
Description: vLLM Mooncake connector through 0.29.0 fails to properly manage GPU KV cache block ownership when concurrent child requests share a single transfer ID in prefill/decode disaggregated deployments. Attackers can trigger GPU memory exhaustion by submitting completion requests with multiple prompts, causing orphaned KV cache blocks to accumulate until process restart and eventually preventing legitimate requests from executing.

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