Junglewise Threat Intelligence

CVE-2026-25048: mlc-ai xgrammar uncontrolled recursion in nested syntax

CVE-2026-25048 · Severity: high · CVSS 7.5 · Published 2026-03-05

Technologies: Red Hat AI Inference Server. Vendors: Red Hat, PyPI.

Executive brief

xgrammar is an open-source library used to ensure that AI models generate structured data, such as JSON or specific code formats. A vulnerability in how the library handles complex, nested instructions can cause the system to crash. This could allow an attacker to disrupt AI services, leading to a denial-of-service (DoS) condition where the AI becomes unavailable to legitimate users.

Technical details

A vulnerability exists in xgrammar prior to version 0.1.32 due to uncontrolled recursion (CWE-674) when parsing multi-level nested syntax. An attacker can exploit this by providing a malicious grammar rule containing deeply nested structures (e.g., 30,000 layers of parentheses), which triggers a stack overflow or memory exhaustion. This results in a segmentation fault and a core dump, leading to a denial-of-service (DoS) of the application utilizing the library. The issue is reachable over the network if the application allows user-defined or complex grammar inputs. The vulnerability has been patched in version 0.1.32.

Affected products

  • mlc-ai xgrammar < 0.1.32
  • Red Hat Red Hat AI Inference Server 3.2.2
  • Red Hat Red Hat OpenShift AI 2.25.7

Timeline

  • 2026-03-04: patched: Version 0.1.32 released
  • 2026-03-05: advisory: GitHub Security Advisory published
  • 2026-03-05: disclosed: CVE-2026-25048 published
  • 2026-03-25: patched: Red Hat AI Inference Server 3.2.2 released

References

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