CVE-2025-32381: Denial of Service by abusing xgrammar unbounded cache in memory
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.
Classification
CVE ID: CVE-2025-32381
CVSS Base Severity: MEDIUM
CVSS Base Score: 6.5
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Products
Vendor: mlc-ai
Product: xgrammar
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.04% (probability of being exploited)
EPSS Percentile: 12.24% (scored less or equal to compared to others)
EPSS Date: 2025-04-21 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-32381https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-389x-67px-mjg3
https://github.com/mlc-ai/xgrammar/pull/243
https://github.com/vllm-project/vllm/pull/16283