CVE-2025-58446: xgrammar DoS — Exploit & Fix

Description

xgrammar is an open-source library for efficient, flexible, and portable structured generation. A grammar optimizer introduced in 0.1.23 processes large grammars (>100k characters) at very low rates, and can be used for DOS of model providers. This issue is fixed in version 0.1.24.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/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	All

References

Advisories & Patches

https://github.com/mlc-ai/xgrammar/commit/ced69c3ad2f8f61b516cc278a342e7c644383e27 https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-9q5r-wfvf-rr7f

Exploits

https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-9q5r-wfvf-rr7f

Frequently Asked Questions

What is CVE-2025-58446? +

xgrammar is an open-source library for efficient, flexible, and portable structured generation. A grammar optimizer introduced in 0.1.23 processes large grammars (>100k characters) at very low rates, and can be used for DOS of model providers. This issue is fixed in version 0.1.24. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-58446? +

CVE-2025-58446 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-58446? +

CVE-2025-58446 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-2025-58446? +

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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