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Vulnerability record · CVE-2025-32381 · published 9 April 2025

CVE-2025-32381: Mlc-ai xgrammar allocation without limits vulnerability

MMlc Ai · Xgrammar

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.

6.5 CVSS 3.1 Medium EPSS 0.50% · top 59.7% CWE-770 · Allocation without limits
6.5CVSS 3.1 base score
0.50%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Source: NIST National Vulnerability Database (record CVE-2025-32381), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.