CVE-2025-59425: vLLM Vulnerable to Timing Attack in API Key Validation
Summary
CVE-2025-59425: vLLM is vulnerable to timing attack at bearer auth. Affects vllm versions < 0.11.0. Fixed in 0.11.0. How to fix ↓
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Background
vLLM is an open-source library designed for efficient and scalable language model serving. It provides a user-friendly API for deploying and interacting with large language models. The library includes built-in support for API key authentication to secure access to its services. However, a vulnerability has been identified in the API key validation mechanism, which could expose users to security risks.
Vulnerability Detail
The vulnerability in vLLM arises from its API key validation process, which utilizes a string comparison method susceptible to timing attacks. This flaw allows attackers to exploit the validation mechanism by measuring the time taken for responses based on the correctness of the characters in the API key. As a result, an attacker could potentially discover valid API keys more efficiently than through brute force methods, leading to unauthorized access to the API.
How To Fix
Latest published version: 0.32.0 as of 22 Oct 2026
pip install --upgrade "vllm==0.32.0"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.11.0
This is the first release that contains the fix.
pip install --upgrade "vllm==0.11.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider implementing additional layers of security, such as rate limiting on API key attempts or using a more secure method for API key validation that does not rely on string comparison. However, the best solution is to update to the patched version.
Conclusion
The vulnerability identified as CVE-2025-59425 in the vLLM package poses significant security risks due to its susceptibility to timing attacks in API key validation. Users are strongly advised to update to the latest version to mitigate these risks and ensure the security of their applications.
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FAQ
A timing attack is a type of side-channel attack where an attacker gains information about a system by measuring the time it takes to execute cryptographic algorithms or operations.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
If exploited, this vulnerability could allow unauthorized users to gain access to your API, potentially leading to data breaches or misuse of your services.
Yes, you can implement rate limiting on API key attempts or use alternative validation methods as a temporary measure until you can update.
The CVSS score for this vulnerability is 7.5, indicating a high severity level.
References
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