CVE-2025-57809: XGrammar is an open-source library for efficient, flexible, and portable structured generation

Q: How do I fix CVE-2025-57809?

xgrammar: upgrade to 0.1.21. Exact commands for each OS are on this page.

Q: Is CVE-2025-57809 being exploited?

CVE-2025-57809 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-57809 affect?

CVE-2025-57809 affects xgrammar. Severity is high (CVSS 7.5). XGrammar is an open-source library for efficient, flexible, and portable structured generation. Prior to version 0.1.21, XGrammar has an infinite recursion issue in the grammar. This issue has been resolved in version 0.1.21.

Q: How urgent is CVE-2025-57809?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2025-57809 is a high-severity flaw (CVSS 7.5) affecting xgrammar. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XGrammar is an open-source library for efficient, flexible, and portable structured generation. Prior to version 0.1.21, XGrammar has an infinite recursion issue in the grammar. This issue has been resolved in version 0.1.21.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-674
Published	2025-08-25
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: mlc-ai

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-08-25 22:15 UTCPublished CVE record published
2026-06-17 09:43 UTCUpdated Record last modified

mlc-ai xgrammar UPGRADE

Affected: < 0.1.21

Fixed in: 0.1.21

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy xgrammar || rpm -q xgrammar || xgrammar --version

2. UPGRADE to 0.1.21 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade xgrammar

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade xgrammar

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-57809?

xgrammar: upgrade to 0.1.21. Exact commands for each OS are on this page.

Is CVE-2025-57809 being exploited?

CVE-2025-57809 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-57809 affect?

CVE-2025-57809 affects xgrammar. Severity is high (CVSS 7.5). XGrammar is an open-source library for efficient, flexible, and portable structured generation. Prior to version 0.1.21, XGrammar has an infinite recursion issue in the grammar. This issue has been resolved in version 0.1.21.

How urgent is CVE-2025-57809?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-25048 HIGH 7.5 UPGRADE xgrammar is an open-source library for efficient, flexible, and portable structured generation
CVE-2025-58446 HIGH 7.5 DOWNGRADE xgrammar is an open-source library for efficient, flexible, and portable structured generation
CVE-2025-32381 MEDIUM 6.5 UPGRADE XGrammar is an open-source library for efficient, flexible, and portable structured generation

References

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