Synopsis
Tenable found multiple unauthenticated, remote stack overflow vulnerabilities in Advantech WebAccess/SCADA 8.4.0.
CVE-2019-3953: Unauthenticated Remote Stack Buffer Overflow (IOCTL 10012)
The flaw exists in viewsrv.dll due to improper validation of user-supplied data before copying the data to a fixed size stack buffer when processing an IOCTL 10012 RPC call.
.text:10001CDC mov esi, [ebp+arg_pInbuf] ; attacker-controlled data .text:10001CDF lea eax, [esi+4] .text:10001CE2 push eax .text:10001CE3 lea ecx, [ebp+var_BroadwinPath] .text:10001CE9 push ecx .text:10001CEA push offset aSSBwextra_ini ; "%s%s\\bwextra.ini" .text:10001CEF lea edx, [ebp+var_file] ; copying attacker-controlled data .text:10001CEF ; to a fixed-size buf on the .text:10001CEF ; stack ==> stack overflow !!! .text:10001CF5 push edx .text:10001CF6 call ds:sprintf
Windbg output:
(2dbd8.2df70): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=00000000 ebx=00000001 ecx=41414141 edx=00000000 esi=00000000 edi=030bd4b4 eip=41414141 esp=030bcec8 ebp=41414141 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 41414141 ?? ??? 0:007> kb ChildEBP RetAddr Args to Child WARNING: Frame IP not in any known module. Following frames may be wrong. 030bcec4 41414141 41414141 41414141 41414141 0x41414141 030bcec8 41414141 41414141 41414141 41414141 0x41414141 030bcecc 41414141 41414141 41414141 41414141 0x41414141 030bced0 41414141 41414141 41414141 41414141 0x41414141 030bced4 41414141 41414141 41414141 41414141 0x41414141 030bced8 41414141 41414141 41414141 41414141 0x41414141 ... 030bcf98 41414141 41414141 77625c41 72747865 0x41414141 030bcf9c 41414141 77625c41 72747865 6e692e61 0x41414141 030bcfa0 77625c41 72747865 6e692e61 00000069 0x41414141 030bcfa4 72747865 6e692e61 00000069 00000000 0x77625c41 030bcfa8 6e692e61 00000069 00000000 00000000 0x72747865 030bcfac 00000000 00000000 00000000 00000000 0x6e692e61 0:007> .load "MSEC.dll" 0:007> !exploitable !exploitable 1.6.0.0 Exploitability Classification: EXPLOITABLE Recommended Bug Title: Exploitable - Data Execution Prevention Violation starting at Unknown Symbol @ 0x0000000041414141 called from Unknown Symbol @ 0x000000006e692e61 (Hash=0x83f3e768.0xed88845e) User mode DEP access violations are exploitable.
CVE-2019-3954: Unauthenticated Remote Stack Buffer Overflow (IOCTL 81024)
The flaw exists in the VdBroadWinGetLocalDataLogEx() function in viewdll1.dll due to improper validation of user-supplied data before copying the data to a fixed-size stack-based buffer when processing an IOCTL 81024 RPC message.
.text:1001671C mov edx, [ebp+var_pNode] ; attacker_controlled .text:10016722 push edx .text:10016723 mov eax, [ebp+var_pProject] ; attacker_controlled .text:10016729 push eax .text:1001672A lea ecx, [ebp+var_ModuleFileName] .text:10016730 push ecx .text:10016731 push offset aSS_SSysinfo_in ; "%s%s_%s\\sysinfo.ini" .text:10016736 lea edx, [ebp+var_634] ; copying attacker-controlled data .text:10016736 ; to a fixed-size buffer on the .text:10016736 ; stack ==> stack overflow! .text:1001673C push edx .text:1001673D call ds:sprintf
Windbg output:
(38084.39638): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=41414141 ebx=0319e674 ecx=00000073 edx=7ffffffe esi=01edb97c edi=41414141 eip=74eed193 esp=0319e3d0 ebp=0319e654 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 msvcrt!_output_l+0x9fd: 74eed193 803800 cmp byte ptr [eax],0 ds:002b:41414141=?? 0:008> kb ChildEBP RetAddr Args to Child 0319e654 74efd399 0319e674 01edb978 00000000 msvcrt!_output_l+0x9fd *** WARNING: Unable to verify checksum for C:\WebAccess\Node\viewdll1.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\WebAccess\Node\viewdll1.dll - 0319e694 01ed67c3 0319e920 01edb978 0319ed44 msvcrt!sprintf+0x5a WARNING: Stack unwind information not available. Following frames may be wrong. 0319ee48 41414141 41414141 41414141 41414141 viewdll1!VdBroadWinGetLocalDataLogEx+0x15a 0319ee4c 41414141 41414141 41414141 41414141 0x41414141 0319ee50 41414141 41414141 41414141 41414141 0x41414141 0319ee54 41414141 41414141 41414141 41414141 0x41414141 ... 0:008> .load msec.dll 0:008> !exploitable !exploitable 1.6.0.0 Exploitability Classification: EXPLOITABLE Recommended Bug Title: Exploitable - Exception Handler Chain Corrupted starting at msvcrt!_output_l+0x00000000000009fd (Hash=0xa92188c6.0xc8febe8f) Corruption of the exception handler chain is considered exploitable
Solution
Upgrade to version 8.4.1 or later.
Disclosure Timeline
04/24/2019 - Vulnerability 1 discovered.
04/25/2019 - Vulnerability reported to Advantech. 90-day date is July 24, 2019.
04/25/2019 - Advantech acknowledges receipt of the information. They will "check it."
04/30/2019 - Advantech states that they will "target a fix around 24 May for this issue."
04/30/2019 - Vulnerability 2 discovered.
05/08/2019 - Vulnerability disclosed to Advantech.
05/08/2019 - Advantech acknowledges receipt of the report and will have an engineer check it out.
05/09/2019 - Advantech will fix both bugs in the same release.
05/09/2019 - Advantech states that they will "expect to fix this in the next release around 24 May".
05/15/2019 - Advantech notifies us that the release will be postponed to May 31.
05/15/2019 - Tenable thanks Advantech for the update.
05/24/2019 - Tenable follows up to see if the bugs fixes are still on track for May 31.
05/26/2019 - Advantech is still targeting May 31, but it is "tight". Will confirm by Wednesday.
05/30/2019 - Advantech has to delay. They will try to release next week.
05/30/2019 - Tenable thanks Advantech for the update.
06/04/2019 - Tenable asks for an update.
06/04/2019 - Advantech pushes release date to June 12, 2019.
06/05/2019 - Tenable thanks Advantech for the update.
06/11/2019 - Tenable follows up to see if the release will go out tomorrow.
06/11/2019 - Advantech hopes to have a release out before the 14th.
06/11/2019 - Tenable thanks Advantech for the update. Informs Advantech of CVE IDs to be assigned.
06/14/2019 - Advantech says they will release 8.4.1 on Monday.
06/14/2019 - Tenable acknowledges.
06/18/2019 - Release notes are posted for 8.4.1. Tenable is unable to download the release notes or a trial installer. Asks Advantech if this version was officially released.
06/18/2019 - Advantech confirms that a patch was released.
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