Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-06T19:49:20 vllm: vLLM: Denial of Service via malformed speculative decoding workload 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-125

vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, a frontend-legal multi-request speculative decoding workload can cause the rejection sampler to produce a recovered token equal to the model vocabulary size boundary value, which is then converted to negative one when the engine selects the next live token for a request and is written back into the drafter's input ids; that out-of-vocabulary value is later consumed by the model's embedding and attention path and crashes the engine worker with a GPU device-side assertion. The same triggering request sequence is reachable through the public gRPC Generate and Abort endpoints, so a remote client that can send generation requests can crash the shared engine worker, aborting concurrent requests and causing a service-wide denial of service for other clients of the deployment until the worker is restarted. This issue is fixed in version 0.24.0.

A flaw was found in vLLM, a high-throughput and memory-efficient inference and serving engine for Large Language Models (LLMs). A remote attacker can exploit this vulnerability by sending a specially crafted multi-request speculative decoding workload through public gRPC Generate and Abort endpoints. This malformed workload can cause the rejection sampler to produce an out-of-vocabulary token, which then crashes the engine worker. This leads to a service-wide Denial of Service (DoS) for all clients until the worker is restarted.

This Important denial of service flaw in vLLM, utilized by Red Hat AI Inference Server, Red Hat Enterprise Linux AI, and Red Hat OpenShift AI, allows a remote attacker to crash the engine worker. By sending a specially crafted multi-request speculative decoding workload to public gRPC endpoints, an attacker can trigger an out-of-vocabulary token, leading to a service-wide disruption for all connected clients. To mitigate this issue, restrict network access to the vLLM inference engine's gRPC Generate and Abort endpoints. Configure firewall rules to limit incoming connections to trusted clients or internal networks only. This will prevent remote, unauthenticated attackers from sending malformed workloads and triggering a denial of service. If the service is exposed via a proxy or load balancer, ensure that access controls are in place at that layer. Red Hat AI Inference Server Will not fix rhaiis/vllm-cpu-rhel9 Red Hat AI Inference Server Affected rhaiis/vllm-cuda-rhel9 Red Hat AI Inference Server Will not fix rhaiis/vllm-neuron-rhel9 Red Hat AI Inference Server Affected rhaiis/vllm-rocm-rhel9 Red Hat AI Inference Server Affected rhaiis/vllm-spyre-rhel9 Red Hat AI Inference Server Will not fix rhaiis/vllm-tpu-rhel9 Red Hat AI Inference Server Affected rhaii/vllm-cpu-rhel9 Red Hat AI Inference Server Affected rhaii/vllm-cuda-rhel9 Red Hat AI Inference Server Will not fix rhaii/vllm-gaudi-rhel9 Red Hat AI Inference Server Will not fix rhaii/vllm-neuron-rhel9 Red Hat AI Inference Server Affected rhaii/vllm-rocm-rhel9 Red Hat AI Inference Server Affected rhaii/vllm-spyre-rhel9 Red Hat AI Inference Server Will not fix rhaii/vllm-tpu-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-aws-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-azure-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-azure-rocm-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-gaudi-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-gcp-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-rocm-rhel9 Red Hat OpenShift AI (RHOAI) Not affected rhoai/odh-kserve-agent-rhel9 Red Hat OpenShift AI (RHOAI) Not affected rhoai/odh-kserve-controller-rhel9 Red Hat OpenShift AI (RHOAI) Not affected rhoai/odh-kserve-router-rhel9 Red Hat OpenShift AI (RHOAI) Not affected rhoai/odh-kserve-storage-initializer-rhel9 Red Hat OpenShift AI (RHOAI) Not affected rhoai/odh-llm-d-kv-cache-rhel9 Red Hat OpenShift AI (RHOAI) Affected rhoai/odh-vllm-gaudi-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-54234 https://nvd.nist.gov/vuln/detail/CVE-2026-54234 https://github.com/vllm-project/vllm/commit/8a5cf1ccd65e8ac7635c402c1ec0b08988bc26ca https://github.com/vllm-project/vllm/pull/44744 https://github.com/vllm-project/vllm/security/advisories/GHSA-8wr5-jm2h-8r4f