vLLM through 0.29.0 Denial of Service via NIXL Multi-Prompt Assertion Failure

Advisories

vLLM through 0.29.0 Denial of Service via NIXL Multi-Prompt Assertion Failure

severity: high
date: 9/21/2026
Affecting: vllm <= 0.29.0
CVE: CVE-2026-94623
CWE: CWE-617 Reachable Assertion
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 #51505
https://github.com/vllm-project/vllm/blob/v0.29.0/vllm/distributed/kv_transfer/kv_connector/v1/nixl/base_worker.py#L2642-L2646
https://github.com/vllm-project/vllm
Credit: Mingkai Yu, Jiapeng Li, Jiajia Liu
Description: vLLM through 0.29.0 contains a denial of service vulnerability in the NIXL connector's prefix caching implementation that fails to properly validate block counts across multi-prompt completion requests in prefill/decode disaggregated deployments. Attackers can trigger an assertion failure in NixlBaseConnectorWorker._apply_prefix_caching by submitting completion requests with multiple prompts of varying lengths, causing the decode worker to terminate and become unavailable until restarted.

Ready to get Started?

Explore VulnCheck, a next-generation Cyber Threat Intelligence platform, which provides exploit and vulnerability intelligence to help you prioritize and remediate vulnerabilities that matter.

Vulnerability Prioritization
Prioritize vulnerabilities that matter based on the threat landscape and defer vulnerabilities that don't.
Early Warning System
Real-time alerting of changes in the vulnerability landscape so that you can take action before the attacks start.

Schedule a Demo