X5 Webserver 5.0 Remote Denial Of Service Exploit

Title: X5 Webserver 5.0 Remote Denial Of Service Exploit
Advisory ID: ZSL-2016-5377
Type: Local/Remote
Impact: DoS
Risk: (3/5)
Release Date: 30.11.2016
X5 is the latest generation web server from iMatix Corporation. The Xitami product line stretches back to 1996. X5 is built using iMatix's current Base2 technology for multithreading applications. On multicore machines, it is much more scalable than Xitami/2.
The vulnerability is caused due to a NULL pointer dereference when processing malicious HEAD and GET requests. This can be exploited to cause denial of service scenario.


(12c0.164c): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
*** WARNING: Unable to verify checksum for C:\zslab\ws\64327\xitami-5.0a0-windows\xitami.exe
*** ERROR: Module load completed but symbols could not be loaded for C:\zslab\ws\64327\xitami-5.0a0-windows\xitami.exe
eax=0070904d ebx=03a91808 ecx=0070904d edx=00000000 esi=0478fef4 edi=0478fe8c
eip=00503ae0 esp=0478fb28 ebp=0478fb48 iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
00503ae0 8b02 mov eax,dword ptr [edx] ds:002b:00000000=????????
0:004> kb
# ChildEBP RetAddr Args to Child
WARNING: Stack unwind information not available. Following frames may be wrong.
00 0478fb48 00460ee6 0ace0840 04025ea0 0478fd78 xitami+0x103ae0
01 0478fe8c 0045f6fa 0ace0bd8 0478ff28 cccccccc xitami+0x60ee6
02 0478fee8 004c60a1 0478ff14 00000000 0478ff38 xitami+0x5f6fa
03 0478ff28 004fdca3 03a90858 03a67e38 00000000 xitami+0xc60a1
04 0478ff40 00510293 03a90858 fc134d7d 00000000 xitami+0xfdca3
05 0478ff7c 00510234 00000000 0478ff94 7679338a xitami+0x110293
06 0478ff88 7679338a 03a91808 0478ffd4 77029902 xitami+0x110234
07 0478ff94 77029902 03a91808 7134bcc2 00000000 kernel32!BaseThreadInitThunk+0xe
08 0478ffd4 770298d5 00510190 03a91808 00000000 ntdll!__RtlUserThreadStart+0x70
09 0478ffec 00000000 00510190 03a91808 00000000 ntdll!_RtlUserThreadStart+0x1b


iMatrix - http://www.xitami.com
Affected Version
Tested On
Microsoft Windows XP Professional SP3 (EN)
Microsoft Windows 7 Ultimate SP1 (EN)
Vendor Status
[15.11.2016] Vulnerability discovered.
[17.11.2016] Vendor contacted.
[29.11.2016] No response from the vendor.
[30.11.2016] Public security advisory released.
Vulnerability discovered by Stefan Petrushevski - <stefan@zeroscience.mk>
[1] https://cxsecurity.com/issue/WLB-2016120003
[2] https://packetstormsecurity.com/files/139963
[3] https://www.exploit-db.com/exploits/40849/
[4] https://exchange.xforce.ibmcloud.com/vulnerabilities/119453
[5] http://www.securiteam.com/exploits/6Q02U1FHRU.html
[30.11.2016] - Initial release
[08.12.2016] - Added reference [1], [2], [3] and [4]
[13.12.2016] - Added reference [5]
Zero Science Lab

Web: http://www.zeroscience.mk
e-mail: lab@zeroscience.mk