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CVE-2025-48956: Denial of Service Vulnerability in vLLM Language Models

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Overview

The CVE-2025-48956 vulnerability is a significant security flaw found in vLLM, an inference and serving engine for large language models. The vulnerability can lead to server memory exhaustion, potentially resulting in a system crash or unresponsiveness. This issue affects versions of vLLM from 0.1.0 to before 0.10.1.1 and can be easily exploited by any remote user making it a significant concern for all users of the affected application.

Vulnerability Summary

CVE ID: CVE-2025-48956
Severity: High (CVSS: 7.5)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System Compromise, Potential Data Leakage

Affected Products

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Product | Affected Versions

vLLM | 0.1.0 to 0.10.1.0

How the Exploit Works

The vulnerability is based on a flaw in the handling of HTTP GET requests by vLLM. When a large header is sent to an HTTP endpoint, the system fails to manage the memory properly, leading to memory exhaustion. This can result in the system becoming unresponsive or crashing entirely. The flaw does not require authentication, allowing any remote user to exploit it.

Conceptual Example Code

This is a conceptual example of how an HTTP GET request might be sent with an excessively large header, triggering the vulnerability.

GET /vulnerable/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/json
X-Custom-Header: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...[continues]

In this example, the `X-Custom-Header` field is filled with an excessively large value, causing the server to exhaust its memory trying to process the request.

Mitigation Guidance

Users are advised to update to vLLM version 0.10.1.1 or later, which contains a fix for the vulnerability. If unable to update immediately, it is recommended to use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to mitigate the risks temporarily.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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