What’s Vulnerable › Vulnerabilities

CVE-2025-46570: vLLM’s Chunk-Based Prefix Caching Vulnerable to Potential Timing Side-Channel

• Severity: low (CVSS 2.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-29 · updated 2026-06-17
• Weakness: CWE-208

Description

vLLM is an inference and serving engine for large language models (LLMs). Prior to version 0.9.0, when a new prompt is processed, if the PageAttention mechanism finds a matching prefix chunk, the prefill process speeds up, which is reflected in the TTFT (Time to First Token). These timing differences caused by matching chunks are significant enough to be recognized and exploited. This issue has been patched in version 0.9.0.

Affected products

• vllm-project vllm: before 0.9.0 — fixed in 0.9.0

How to fix

Upgrade to a fixed version: vllm-project vllm 0.9.0. Check the vendor advisory for mitigations.

References

• https://github.com/vllm-project/vllm/commit/77073c77bc2006eb80ea6d5128f076f5e6c6f54f
• https://github.com/vllm-project/vllm/pull/17045
• https://github.com/vllm-project/vllm/security/advisories/GHSA-4qjh-9fv9-r85r

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