CVE-2025-32381: xgrammar DoS — Fix

Description

XGrammar is an open-source library for efficient, flexible, and portable structured generation. Prior to 0.1.18, Xgrammar includes a cache for compiled grammars to increase performance with repeated use of the same grammar. This cache is held in memory. Since the cache is unbounded, a system making use of xgrammar can be abused to fill up a host's memory and case a denial of service. For example, sending many small requests to an LLM inference server with unique JSON schemas would eventually cause this denial of service to occur. This vulnerability is fixed in 0.1.18.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-770 CWE-770

Affected Products

Vendor	Product	Versions
mlc-ai	xgrammar	< 0.1.18

References

Advisories & Patches

https://github.com/mlc-ai/xgrammar/pull/243 https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-389x-67px-mjg3 https://github.com/vllm-project/vllm/pull/16283

Frequently Asked Questions

What is CVE-2025-32381? +

XGrammar is an open-source library for efficient, flexible, and portable structured generation. Prior to 0.1.18, Xgrammar includes a cache for compiled grammars to increase performance with repeated use of the same grammar. This cache is held in memory. Since the cache is unbounded, a system making use of xgrammar can be abused to fill up a host's memory and case a denial of service. For example, sending many small requests to an LLM inference server with unique JSON schemas would eventually cause this denial of service to occur. This vulnerability is fixed in 0.1.18. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2025-32381? +

CVE-2025-32381 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-32381? +

CVE-2025-32381 affects products from mlc-ai, specifically: xgrammar. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-32381? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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