CVE-2025-48956

A Denial of Service (DoS) vulnerability can be triggered by sending a single HTTP GET request with an extremely large header to an HTTP endpoint. This results in server memory exhaustion, potentially leading to a crash or unresponsiveness. The attack does not require authentication, making it exploitable by any remote user.

Details

The vulnerability leverages the abuse of HTTP headers. By setting a header such as X-Forwarded-For to a very large value like ("A" * 5_800_000_000), the server's HTTP parser or application logic may attempt to load the entire request into memory, overwhelming system resources.

Resolution

Upgrade to a version of vLLM that includes appropriate HTTP limits by deafult, or use a proxy in front of vLLM which provides protection against this issue.

What kind of vulnerability is it? Who is impacted?
Type of vulnerability: Denial of Service (DoS)

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2025-48956 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.10.1.1); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-48956? CVE-2025-48956 is a high-severity uncontrolled resource consumption vulnerability in vllm (pip), affecting versions >= 0.1.0, < 0.10.1.1. It is fixed in 0.10.1.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2025-48956? CVE-2025-48956 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of vllm are affected by CVE-2025-48956? vllm (pip) versions >= 0.1.0, < 0.10.1.1 is affected.
4. Is there a fix for CVE-2025-48956? Yes. CVE-2025-48956 is fixed in 0.10.1.1. Upgrade to this version or later.
5. Is CVE-2025-48956 exploitable, and should I be worried? Whether CVE-2025-48956 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-48956 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-48956? Upgrade vllm to 0.10.1.1 or later.