CVE-2025-57809
📋 TL;DR
CVE-2025-57809 is an infinite recursion vulnerability in XGrammar library versions before 0.1.21. This allows attackers to cause denial of service (DoS) by triggering uncontrolled recursion that consumes system resources. Any application using vulnerable XGrammar versions for structured generation is affected.
💻 Affected Systems
- XGrammar library
📦 What is this software?
Xgrammar by Mlc Ai
⚠️ Risk & Real-World Impact
Worst Case
Complete system resource exhaustion leading to denial of service, potentially crashing the application or host system.
Likely Case
Application instability, performance degradation, or service disruption when processing malicious grammar inputs.
If Mitigated
Minimal impact with proper input validation and resource limits in place.
🎯 Exploit Status
Exploitation requires crafting specific grammar inputs that trigger infinite recursion, which is relatively straightforward for knowledgeable attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.1.21
Vendor Advisory: https://github.com/mlc-ai/xgrammar/security/advisories/GHSA-5cmr-4px5-23pc
Restart Required: Yes
Instructions:
1. Identify XGrammar version in your environment
2. Update to version 0.1.21 or later using package manager
3. Restart any services using XGrammar
4. Test grammar processing functionality
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict input validation to reject potentially malicious grammar structures before processing
Resource limiting
allConfigure recursion depth limits and timeout mechanisms in applications using XGrammar
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Deploy application-level firewalls to filter suspicious grammar inputs
🔍 How to Verify
Check if Vulnerable:
Check XGrammar version in package manifest or run 'pip show xgrammar' for Python installationsCheck Version:
pip show xgrammar | grep VersionVerify Fix Applied:
Confirm version is 0.1.21 or later and test with known problematic grammar inputs📡 Detection & Monitoring
Log Indicators:
- Unusual recursion depth warnings
- Process termination due to resource exhaustion
- Abnormal CPU/memory spikes during grammar processing
Network Indicators:
- Repeated grammar processing requests from single sources
- Unusually large grammar payloads
SIEM Query:
source="application.logs" AND ("recursion depth exceeded" OR "memory limit" OR "xgrammar")