CVE-2025-58446: xgrammar is an open-source library for efficient, flexible, and portable structured generation

This week

HIGH 7.5REMOTEDOWNGRADE

CVE-2025-58446 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. 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.

Why this priority

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

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-770
Published	2025-09-06
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

2025-09-06 19:15 UTCPublished CVE record published
2026-06-17 09:44 UTCUpdated Record last modified

mlc-ai xgrammar DOWNGRADE

Affected: 0.1.23

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.1.23

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.1.23 (Debian / Ubuntu)

apt-cache madison xgrammar sudo apt install xgrammar=<VERSION_BEFORE_0.1.23> sudo apt-mark hold xgrammar

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list xgrammar sudo dnf downgrade xgrammar-<VERSION_BEFORE_0.1.23> sudo dnf versionlock add xgrammar

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2025-58446?

xgrammar: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-58446 being exploited?

CVE-2025-58446 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-2025-58446 affect?

CVE-2025-58446 affects xgrammar. Severity is high (CVSS 7.5). 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 provide

How urgent is CVE-2025-58446?

Priority 49/100. 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-2025-57809 HIGH 7.5 UPGRADE 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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