How severe is CVE-2025-57809?

No CVSS score has been assigned to CVE-2025-57809 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-57809?

CVE-2025-57809 affects the following packages: xgrammar (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-57809?

Update xgrammar to 0.1.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-57809 is resolved across your whole dependency graph.

How do I detect CVE-2025-57809 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for xgrammar, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-57809 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2025-57809?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-57809 can be triaged on real exposure rather than presence alone.

Is CVE-2025-57809 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-57809 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-57809?

CVE-2025-57809 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 39th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-57809?

CVE-2025-57809 is classified as CWE-674 (CWE-674). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-57809 published, and has it been updated?

CVE-2025-57809 was published on August 25, 2025 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2025-57809 — xgrammar

Fix: mlc-ai/xgrammar@b943fea

CVE-2025-57809 is a CWE-674 vulnerability in xgrammar. A fix is available for xgrammar — see the affected versions and patch details below.

XGrammar affected by Denial of Service by infinite recursion grammars

Also known asGHSA-5cmr-4px5-23pcPYSEC-2026-2054

Published

Aug 25, 2025

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-57809.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

🐍xgrammar

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

This issue: http://github.com/mlc-ai/xgrammar/issues/250 should have it's own security advisory. Since several tools accept and pass user supplied grammars to xgrammar, and it is so easy to trigger it seems like a High.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`xgrammar`	all versions	0.1.21`pip install --upgrade 'xgrammar==0.1.21'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for xgrammar, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update xgrammar to 0.1.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-57809 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-57809 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2025-57809. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This vulnerability is considered Important because it can be exploited remotely, without authentication or user interaction, and directly impacts the availability of systems that rely on xgrammar for structured output parsing. Unlike a Moderate flaw that might require unusual conditions or only cause partial…

Product	Fixed in	Advisory
Red Hat Enterprise Linux AI 1.5	`rhelai1/instructlab-intel-rhel9:1.5.4-1761050413`	RHSA-2025:19421
Red Hat Enterprise Linux AI 1.5	`rhelai1/bootc-intel-rhel9:1.5.4-1761060689`	RHSA-2025:19422
Red Hat Enterprise Linux AI 1.5	`rhelai1/instructlab-nvidia-rhel9:1.5.4-1761220254`	RHSA-2025:19423
Red Hat Enterprise Linux AI 1.5	`rhelai1/bootc-azure-amd-rhel9:1.5.4-1761073793`	RHSA-2025:19424
Red Hat Enterprise Linux AI 1.5	`rhelai1/instructlab-amd-rhel9:1.5.4-1761043227`	RHSA-2025:19425
Red Hat Enterprise Linux AI 1.5	`rhelai1/bootc-gcp-nvidia-rhel9:1.5.4-1761236079`	RHSA-2025:19426
Red Hat Enterprise Linux AI 1.5	`rhelai1/bootc-amd-rhel9:1.5.4-1761064179`	RHSA-2025:19427
Red Hat Enterprise Linux AI 1.5	`rhelai1/bootc-nvidia-rhel9:1.5.4-1761228838`	RHSA-2025:19428

Frequently Asked Questions

### Summary This issue: http://github.com/mlc-ai/xgrammar/issues/250 should have it's own security advisory. Since several tools accept and pass user supplied grammars to xgrammar, and it is so easy to trigger it seems like a High.

O3 Security · Impact-Aware SCA

Is CVE-2025-57809 in your dependencies?

O3 Security finds CVE-2025-57809 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works