Workstation Service NetpManageIPCConnect Buffer Overflow Release Date:
November 14, 2006

Date Reported:
July 25, 2006

Patch Development Time (In Days):

		112

Severity:
High (Remote Code Execution)

Vendor:
Microsoft

Systems Affected:
Windows 2000 (Remote Code Execution)
Windows XP SP1 (Local Privilege Escalation)

Overview:
A flaw exists in a default Windows component called the "Workstation Service" that when exploited allows for remote code execution in SYSTEM context, allowing an attacker to take complete control of affected systems.

Technical Details:
In the Workstation Service module called wkssvc.dll, the NetpManageIPCConnect function has a call to "swprintf" with an unchecked buffer. The input buffer is controllable by the remote attacker.

.text:76781D67 mov edi, [ebp+arg_0]
...
.text:76781D90 lea eax, [ebp+var_2CC]
...
.text:76781DA0 push edi
.text:76781DA1 push offset "%ws\\IPC$"
.text:76781DA6 push eax
.text:76781DA7 call ds:swprintf

This function is called by NetpJoinDomain, which is eventually called by the NetrJoinDomain2 function, which is exposed through RPC.

The IDL for NetrJoinDomain2 looks like this:
long _NetrJoinDomain2@28 (
[in][unique][string] wchar_t * arg_1,
[in][string] wchar_t * arg_2,
[in][unique][string] wchar_t * arg_3,
[in][unique][string] wchar_t * arg_4,
[in][unique] struct_C * arg_5,
[in] long arg_6
);

arg_2 will contain string with format like <Domain name>+"\"+<Hostname>.

<Hostname> will be passed as NetpManageIPCConnect's first argument. The variable is under the attacker's control and is passed to swprintf, which causes a stack-based buffer overflow.

For this vulnerable code to be reached, we must provide a valid and live <Domain name> as a part of the string. We can set up a fake domain server anywhere reachable from the vulnerable machine on the Internet.

Protection:
Blink - Unified Client Security has proactively protected from this vulnerability since its discovery.
Retina - Network Security Scanner has been updated to identify this vulnerability.

Vendor Status:
Microsoft has released a patch for this vulnerability. The patch is available at:
http://www.microsoft.com/technet/security/bulletin/ms06-070.mspx

Credit:
Discovery: JeongWook Matt Oh
Additional Research: Derek Soeder

Related Links:
Retina - Network Security Scanner - Free Trial

Blink - Unified Client Security Personal - Free For Home Use

Blink - Unified Client Security Professional - Free Trial

Greetings:
Dugsong, Ohhara, Ryan Lee, Pilot, Sakai, Gonan and all the Korean Bugtruck Mailing List Subscribers

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