Vulnerability · Published Sep 21, 2026 · Assigned by VulnCheck

CVE-2026-94623vLLM through 0.29.0 Denial of Service via NIXL Multi-Prompt Assertion Failure

High 7.5

In plain English

A high-severity security flaw in vllm from vllm-project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.6%top 49.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	vllm	0.30.0	PYSEC-2026-4005

Affected products (as reported)

Vendor	Product	Versions
vllm-project	vllm	0 – through 0.29.0

Weakness: CWE-617 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Pull Request #51505 issue-tracking, patch
https://github.com/vllm-project/vllm/blob/v0.29.0/vllm/distributed/kv_transfer/kv_connector/v1/nixl/base_worker.py#L2642-L2646 technical-description
https://github.com/vllm-project/vllm product
VulnCheck Advisory: vLLM through 0.29.0 Denial of Service via NIXL Multi-Prompt Assertion Failure third-party-advisory