Trend Micro ServerProtect StCommon.dll Stack Overflow Vulnerabilities

These vulnerabilities allow attackers to execute arbitrary code on vulnerable installations of Trend Micro ServerProtect. Authentication is not required to exploit these vulnerabilities.

The specific flaws exist within the StCommon.dll library and are reachable remotely through a DCE/RPC endpoint on TCP port 5168 bound to by the service SpntSvc.exe. The RPC endpoint is exposed from TmRpcSrv.dll with the following IDL stub information:

    // opcode:  0x00, address: 0x65741030
    // uuid:    25288888-bd5b-11d1-9d53-0080c83a5c2c
    // version: 1.0
    error_status_t   rpc_opnum_0 (
     [in] handle_t  arg_1,
     [in] long  trend_req_num,
     [in][size_is(arg_4)] byte overflow_str[],
     [in] long  arg_4,
     [out][size_is(arg_6)] byte arg_5[],
     [in] long  arg_6

The upper half of the 'trend_req_num' DWORD RPC argument from above is used within TmRpcSrv.dll as an index into a call table. It must specifically be 0x000a which results in a call to StRpcSrv.65673970(). The original arguments to the RPC endpoint are then passed to this called routine:

    657416E6     mov eax, opnum0_call_table[eax*4]
    657416ED     test eax, eax
    657416EF     jnz short loc_65741707
    65741707 loc_65741707:
    65741707     mov [ebp+var_4], 0
    6574170E     mov edx, [ebp+sizeof_arg5]
    65741711     push edx
    65741712     mov edx, [ebp+arg5_array]
    65741715     push edx
    65741716     mov edx, [ebp+sizeof_overflow_str]
    65741719     push edx
    6574171A     mov edx, [ebp+overflow_str]
    6574171D     push edx
    6574171E     push ecx       ; trend_req_num
    6574171F     call eax       ; call handler

The lower half of the 'trend_req_num' DWORD RPC argument is then used within StRpcSrv.dll as an index into a second call table. The value of this lower half controls the code flow to the following vulnerabilities and is hereto referred to as the 'subcode'.

A subcode value of either 0x0011 or 0x0017 results in the following call:

    65674D7F push ebx   ; overflow_str
    65674D80 call CMON_NetTestConnection

A stack overflow occurs within the routine CMON_NetTestConnection() due to an unbounded widechar wsprintf() into a 44 byte stack based buffer as shown in the following relevant excerpt:

    65634AC5 xor ecx, ecx
    65634AC7 lea edx, [esp+65Ch+Name] ; 44 byte stack buffer
    65634ACB mov cx, [eax]
    65634ACE push ecx
    65634ACF push ebx                 ; 1st arg
    65634AD0 push offset str_SC       ; "\\\\%s\\%c$"
    65634AD5 push edx                 ; LPWSTR
    65634AD6 call ds:wsprintfW        ; vuln!

A subcode value of either 0x0008 or 0x0009 results in calls to CMON_ActiveUpdate() and CMON_ActiveRollback() respectively. Both of these routines subsequently call StCommon.65631220() which can result in a stack overflow due to an unbounded widechar lstrcat() into a 2k stack-based buffer as shown in the following relevant excerpt:

    65631311 lea edx, [esp+0A78h+buf]
    65631318 push ebp                 ; lpString2
    65631319 push edx                 ; lpString1
    6563131A call ebx ; lstrcatW      ; stack overflow

The resulting stack overflows can be leveraged to execute arbitrary code under the privileges of the SYSTEM user.

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