An exploitable code execution vulnerability exists in the NewProducerStream functionality of Natus Xltek NeuroWorks 8. A specially crafted network packet can cause a stack buffer overflow resulting in code execution. An attacker can send a malicious packet to trigger this vulnerability.
Natus Xltek NeuroWorks 8
10.0 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE-121: Stack-based Buffer Overflow
Natus NeuroWorks 8 provides a networking solution for the Natus Xltek EEG products. In particular, it is used to monitor and review study data from anywhere on the network. This advisory looks into the NWStorage service bundled with NeuroWorks.
The modules used in this advisory are shown below:
0:006> lm vm Storage start end module name 00400000 00471000 storage (deferred) Image path: c:\Neuroworks\storage.exe Image name: storage.exe Timestamp: Wed Nov 06 10:11:09 2013 (527A863D) CheckSum: 0006EC3D ImageSize: 00071000 File version: 184.108.40.2064 Product version: 220.127.116.114
One of the key data structures in Neuroworks is the KeyTree. Internally, a KeyTree is a List of Lists. The List and KeyTree structs are shown below:
KeyTree/List char opcode; // 5 for KeyTree, 4 for ItemList int num_elements ; // Number of elements in this KeyTree Item[num_elements] items; // List of elements
During the processing of the
NewProducerStream command, a client supplied KeyTree is parsed looking for a
SlowReviewLocalPath key. This extraction is shown below:
.text:00434F01 push offset aSlowreviewloca ; "SlowReviewLocalPath" .text:00434F06 mov this, ebx .text:00434F08 call edi ; CKeyTree::GetAt(char const *)  .text:00434F0A mov this, eax .text:00434F0C call ds:CItem::AsCStr(char const *)  .text:00434F12 mov [esp+364h+var_4], 6 .text:00434F1D lea this, [esp+364h+stLocalPath] .text:00434F21 call ds:ATL::CSimpleStringT<char,1>::GetLength(void)  .text:00434F27 test eax, eax
The actual item is returned,  and cast into a C string, . Finally its length is checked to be non zero to ensure there is data to be processed, . This data is then passed through a combination of splitpath and makepath shown below.
.text:00434FBF lea this, [esp+368h+fname] //user controlled  .text:00434FC6 push this ; Filename .text:00434FC7 lea this, [esp+36Ch+stLocalPath] .text:00434FCB call ds:ATL::CSimpleStringT<char,1>::operator char const *(void) .text:00434FD1 push eax ; Dir .text:00434FD2 lea edx, [esp+370h+filename]  .text:00434FD6 push 0 ; Drive .text:00434FD8 push edx ; Path .text:00434FD9 call ds:__imp___makepath
The resulting makepath call will put the entire filename into the filename local variable, . However the user supplied string, , is not checked to ensure it does not overstep this boundary. This results in a stack based buffer overflow and an exception triggered. Due to the overflow the exception handlers have been overwritten giving direct control of the program.
(abc.668): 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=00000000 ecx=deadbeef edx=77f06d8d esi=00000000 edi=00000000 eip=deadbeef esp=0012f298 ebp=0012f2b8 iopl=0 nv up ei pl zr na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010246 deadbeef ?? ???
2017-07-15 - Initial vendor contact
2017-10-06 - Vendor Acknowledged
2018-04-04 - Public Release
Discovered by Cory Duplantis and Tyler Bohan of Cisco Talos.