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X5 Webserver 5.0 Remote Denial Of Service Exploit

Medium
Advisory ID
ZSL-2016-5377
Release Date
30 November 2016
Vendor
Affected Version
5.0a0
CVE
N/A
Tested On
Microsoft Windows XP Professional SP3 (EN), Microsoft Windows 7 Ultimate SP1 (EN)
Summary

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.

Description

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 xitami+0x103ae0: 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
Proof of Concept
Disclosure Timeline
15.11.2016Vulnerability discovered.
17.11.2016Vendor contacted.
29.11.2016No response from the vendor.
30.11.2016Public security advisory released.
Credits
Vulnerability discovered by Stefan Petrushevski
References
Changelog
30.11.2016Initial release
08.12.2016Added reference [1], [2], [3] and [4]
13.12.2016Added reference [5]