HIGH7.5

PYSEC-2026-2054

XGrammar affected by Denial of Service by infinite recursion grammars

Quick fix

PYSEC-2026-2054 — xgrammar: upgrade to the fixed version with the command below.

pip install --upgrade 'xgrammar>=0.1.21'

Details

### 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.

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/xgrammar

Introduced in: 0Fixed in: 0.1.21

Fixpip install --upgrade 'xgrammar>=0.1.21'

References

https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-5cmr-4px5-23pc[WEB]
https://nvd.nist.gov/vuln/detail/CVE-2025-57809[ADVISORY]
https://github.com/mlc-ai/xgrammar/issues/250[WEB]
https://github.com/mlc-ai/xgrammar/commit/b943feacb5a1caf4d39de8ec3bf7c7ce066dcee5[WEB]
https://github.com/mlc-ai/xgrammar[PACKAGE]
https://pypi.org/project/xgrammar[PACKAGE]
https://github.com/advisories/GHSA-5cmr-4px5-23pc[ADVISORY]