Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/38745539b71cf201bb502437f891d799.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Ransom Lockbit 3.0
Vulnerability: Local Unicode Buffer Overflow (SEH)
Description: The ransomware apparently now requires a password to execute as noted by "@vxunderground" E.g. "-pass db66023ab2abcb9957fb01ed50cdfa6a", but doesnt properly check bounds for both the -pass and -k arguments. Supplying a long string of characters for either flag will trigger a unicode stack buffer overflow overwriting the ECX register and structured exception handler (SEH). 
Family: Lockbit
Type: PE32
MD5: 38745539b71cf201bb502437f891d799
Vuln ID: MVID-2022-0620
ASLR: False
DEP: True
CFG: False
Safe SEH: False
Disclosure: 07/03/2022

Memory Dump:
(b4.1c38): Access violation - code c0000005 (first/second chance not available)
eax=6bce1634 ebx=00000000 ecx=00410041 edx=77729d70 esi=00000000 edi=00000000
eip=a291273d esp=000a12f8 ebp=000a1318 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
a291273d ??              ???

0:000> .ecxr
eax=6bce1634 ebx=00000000 ecx=00410041 edx=77729d70 esi=00000000 edi=00000000
eip=a291273d esp=000a12f8 ebp=000a1318 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
a291273d ??              ???

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

Failed calling InternetOpenUrl, GLE=12029

FAULTING_IP: 
LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce+1b21e
0041b21e f366a5          rep movs word ptr es:[edi],word ptr [esi]

EXCEPTION_RECORD:  0019f688 -- (.exr 0x19f688)
ExceptionAddress: 0041b21e (LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce+0x0001b21e)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000001
   Parameter[1]: 001a0000
Attempt to write to address 001a0000

PROCESS_NAME:  LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce.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:  00000008

EXCEPTION_PARAMETER2:  a291273d

WRITE_ADDRESS:  a291273d 

FOLLOWUP_IP: 
+1b21e
a291273d ??              ???

FAILED_INSTRUCTION_ADDRESS: 
+1b21e
a291273d ??              ???

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

IP_ON_HEAP:  a291273d
The fault address in not in any loaded module, please check your build's rebase
log at <releasedir>\bin\build_logs\timebuild\ntrebase.log for module which may
contain the address if it were loaded.

CONTEXT:  0019f6d8 -- (.cxr 0x19f6d8)
eax=00000020 ebx=0019fc00 ecx=0000004a edx=0000029a esi=025724f4 edi=001a0000
eip=0041b21e esp=0019fb38 ebp=0019fb48 iopl=0         nv up ei pl zr na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010246
LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce+0x1b21e:
0041b21e f366a5          rep movs word ptr es:[edi],word ptr [esi]
Resetting default scope

ADDITIONAL_DEBUG_TEXT:  Followup set based on attribute [Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD]

LAST_CONTROL_TRANSFER:  from 0041b26a to 0041b21e

FAULTING_THREAD:  ffffffff

DEFAULT_BUCKET_ID:  STACKIMMUNE

PRIMARY_PROBLEM_CLASS:  STACKIMMUNE

BUGCHECK_STR:  APPLICATION_FAULT_STACKIMMUNE_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_00410041

STACK_TEXT:  
00000000 00000000 lockbit3+0x0


STACK_COMMAND:  .cxr 000000000019F6D8 ; kb ; ** Pseudo Context ** ; kb

SYMBOL_NAME:  lockbit3

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: lockbit3

IMAGE_NAME:  lockbit3

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:  STACKIMMUNE_c0000005_lockbit3!Unloaded

BUCKET_ID:  APPLICATION_FAULT_STACKIMMUNE_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_00410041_BAD_IP_lockbit3

Followup: MachineOwner
---------

0:000> !exchain
0019f59c: ntdll!ExecuteHandler2+44 (77729d70)
0019ffcc: LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce+10041 (00410041)
Invalid exception stack at 00410041



Exploit/PoC:
from subprocess import Popen

#Discovery/Credits: malvuln
#Vulnerability: Unicode Buffer Overflow (SEH)
#Disclosure: 07/03/2022
#Hash: 80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce
#MD5: 38745539b71cf201bb502437f891d799
#================================================================================================
#
#Apparently Lockbit 3.0 - Lockbit Black (aka LockShit), now requires a password to execute E.g.
#
#vx-underground commented on 2022-07-03 18:55:48 UTC
#
#{04830965-76E6-6A9A-8EE1-6AF7499C1D08}.exe -k LocalServiceNetworkRestricted -pass db66023ab2abcb9957fb01ed50cdfa6a
#
#https://bazaar.abuse.ch/sample/80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce/
#===============================================================================================
#
#Supplying a long payload of characters for the -pass or -k switches triggers a Buffer Overflow.
#===============================================================================================

TARGET="LockBit3_80e8defa5377018b093b5b90de0f2957f7062144c83a09a56bba1fe4eda932ce.exe"
BANNER="""
    __               __   _____ __    _ __ 
   / /   ____  _____/ /__/ ___// /_  (_) /_
  / /   / __ \/ ___/ //_/\__ \/ __ \/ / __/
 / /___/ /_/ / /__/ ,<  ___/ / / / / / /_  
/_____/\____/\___/_/|_|/____/_/ /_/_/\__/  3.0
                                           
                        Unicode Buffer Overflow
                        By malvuln
"""

PAYLOAD="A"*666

def doit():
    Popen([TARGET, "-pass", PAYLOAD], shell=True)

if __name__=="__main__":
    print(BANNER)
    doit()



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