vllm API endpoints vulnerable to Denial of Service Attacks
Summary
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.
Impact
What kind of vulnerability is it? Who is impacted? Type of vulnerability: Denial of Service (DoS)
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | vllm | >= 0.1.0, < 0.10.1.1 | 0.10.1.1 |
References
- https://github.com/vllm-project/vllm/security/advisories/GHSA-rxc4-3w6r-4v47
- https://nvd.nist.gov/vuln/detail/CVE-2025-48956
- https://github.com/vllm-project/vllm/pull/23267
- https://github.com/vllm-project/vllm/commit/d8b736f913a59117803d6701521d2e4861701944
- https://github.com/vllm-project/vllm
- https://pypi.org/project/vllm
- https://github.com/advisories/GHSA-rxc4-3w6r-4v47
- https://github.com/pypa/advisory-database/tree/main/vulns/vllm/PYSEC-2026-2021.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
vllm- Disclosed
- 21.08.2025
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2021 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-rxc4-3w6r-4v47 - CC BY 4.0
Vulnerability history: vllm
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 94
- First → latest
- 09.2024 10.2026
- Without a fix
- 5
- Exploited in attacks
- 0
Severity breakdown
- Critical 9
- High 23
- Medium 47
- Low 4
- Unrated 11
Disclosures per year
- 2024: 2
- 2025: 30
- 2026: 62
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vllm API endpoints vulnerable to Denial of Service Attacks this entry
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