Denial of Service Vulnerability in vLLM by vLLM Project

CVE-2026-94623

What is CVE-2026-94623?

The vLLM library, up to version 0.29.0, is susceptible to a denial of service vulnerability stemming from the NIXL connector's prefix caching mechanism. This vulnerability arises from inadequate validation of block counts during multi-prompt completion requests in disaggregated deployments. Attackers can exploit this flaw by sending specially crafted requests with multiple prompts of varying lengths, which leads to an assertion failure in the NixlBaseConnectorWorker._apply_prefix_caching function. As a result, the decode worker may terminate unexpectedly, rendering it unavailable until a restart occurs.

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