[Full-disclosure] [EEYEB-20060703] IBM eGatherer ActiveX Code Execution Vulnerability

2006-08-1700:00:00

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IBM eGatherer ActiveX Code Execution Vulnerability

Release Date:
August 16, 2006

Date Reported:
July 3, 2006

Patch Development Time (in days):
44

Severity:
High (Remote Code Execution)

Vendor:
IBM / Lenovo

Systems Affected:
Windows NT 4.0 (All versions)
Windows 2000 (All versions)
Windows XP (All versions)
Windows 2003 (All versions)

Overview:
eEye Digital Security has discovered a security vulnerability in IBM's
eGatherer ActiveX control. This is the second vulnerability found in
this control by eEye Research, the first being from Drew Copley
(http://www.eeye.com/html/research/advisories/AD20040615B.html). This
control is typically installed by default on IBM workstations and
laptops, and is used by default for auto-finding drivers/updates on
IBM's/Lenovo's support site.

IBM / Lenovo describes this ActiveX control as follows:
"The auto-detect feature automatically finds your system's machine-type,
model, and serial number to help you get the files and information you
need quickly and easily. It does not collect any personal information
or compromise the security of your system in any way."

Despite their promise for not "comprimising the security of the system
in any way", a buffer overflow exists within the handling of a parameter
of the ActiveX control that would allow a remote attacker to reliably
overwrite the stack with arbitrary data and execute arbitrary code
through the web browser with the privileges of the logged in user.

Technical Details:
The vulnerability exists within the RunEgatherer functionwithin the
ActiveX. This method accepts one function, the specified file name for
the eGatherer log output. It should be noted that even when setting the
parameter with legitimate paths for output, the ActiveX remains to only
write the log file to the SystemDrive. By filling the single paramater
with a large string, a straight stack overflow occurs. The following
sample would reproduce the crash for vulnerable ActiveX controls:

##<html>
##<object classid='clsid:74FFE28D-2378-11D5-990C-006094235084'
id='notCompromising'></object>
##<script language='vbscript'>
##overflowBuffer=String(300,"A")
##notCompromising.RunEgatherer overflowBuffer
##</script>

The vulnerable code is as follows:

.text:10003B73 push dword ptr [ebp+0Ch] ; lpString
.text:10003B76 call ds:lstrlenW
.text:10003B7C lea edi, [eax+eax+2]
.text:10003B80 mov eax, edi
.text:10003B82 add eax, 3
.text:10003B85 and al, 0FCh
.text:10003B87 call __alloca_probe
.text:10003B8C mov esi, esp
.text:10003B8E push ebx ; lpUsedDefaultChar = 0x0
.text:10003B8F push ebx ; lpDefaultChar = 0x0
.text:10003B90 push edi ; cchMultiByte = 1002 (eax*2 + 2)
.text:10003B91 push esi ; lpMultiByteStr = ESP (STACK)
.text:10003B92 push 0FFFFFFFFh ; cchWideChar = -1
.text:10003B94 push dword ptr [ebp+0Ch] ; lpWideCharStr = ptr to our
string
.text:10003B97 mov [esi], bl
.text:10003B99 push ebx ; dwFlags = 0x0
.text:10003B9A push ebx ; CodePage = 0x0
.text:10003B9B call ds:WideCharToMultiByte

The vulnerability begins with a stack allocation for the string. This
is not in itself vulnerable, but there has yet to be a length check the
supplied string.
The string is copied again one more into memory, slightly below the
first, and then lower-cased:

.text:10003BA1 lea eax, [ebp-118h]
.text:10003BA7 push esi ; unsigned __int8 *
.text:10003BA8 mov esi, ds:_mbscpy
.text:10003BAE push eax ; unsigned __int8 *
.text:10003BAF call esi ; _mbscpy
.text:10003BB1 lea eax, [ebp-118h]
.text:10003BB7 pop ecx
.text:10003BB8 test eax, eax
.text:10003BBA pop ecx
.text:10003BBB jz short loc_10003C23
.text:10003BBD lea eax, [ebp-118h]
.text:10003BC3 push eax ; unsigned __int8 *
.text:10003BC4 call sub_10003C45 ; TOLOWER SUBROUTINE

The original string remains untouched, and all future operations will be
performed on the lower-case string. However, because there were no
length checks on the string, the memory is copied straight into the
undersized stack buffer and causes a simple buffer overflow.

Protection:
Retina (http://www.eeye.com/html/Products/Retina/index.html) Network
Security Scanner has been updated to identify this vulnerability.
Blink (http://www.eeye.com/html/products/blink/index.html) Endpoint
Vulnerability Prevention preemptively protects from this vulnerability.

Vendor Status:
IBM UK has patched the vulnerability in their latest version of the
eGatherer ActiveX control (3.20.0284.0), available here:
http://www-307.ibm.com/pc/support/IbmEgath.cab.

Credit:
Andre Derek Protas

Greetings:
Barnz,D-Rock,Karl,HTP,Marc,Steve,Tequila,Ica,SyScan06,xbxice,The
Fam-Damnly, and (RIT(D|S))+.

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