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Category:   Application (Security)  >   Trend Micro Internet Security Vendors:   Trend Micro
PC-cillin Unsafe 'TmComm.sys' Driver Permissions Let Local Users Gain Elevated Privileges
SecurityTracker Alert ID:  1017604
SecurityTracker URL:
CVE Reference:   CVE-2007-0856   (Links to External Site)
Updated:  May 19 2008
Original Entry Date:  Feb 7 2007
Impact:   Execution of arbitrary code via local system, Root access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2007
Description:   A vulnerability was reported in PC-cillin. A local user can obtain kernel level privileges on the target system.

The TmComm DOS device interface ('TmComm.sys') permissions allow users in the 'Everyone' group to write to the device. A local user can exploit this to execute arbitrary commands on the target system with kernel level privileges.

The Anti-Rootkit Common Module (RCM) component is affected.

The vendor was notified on January 17, 2007.

Ruben Santamarta discovered this vulnerability.

Impact:   A local user can obtain kernel level privileges on the target system.
Solution:   The vendor has issued a fixed version (Anti-Rootkit Common Module [RCM] version 1.600-1052), available automatically via the Automatic Update or manually via the "Update Now" function.

The Trend Micro advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Access control error
Underlying OS:  Windows (Any)

Message History:   None.

 Source Message Contents

Subject:  iDefense Security Advisory 02.07.07: Trend Micro TmComm Local

Trend Micro TmComm Local Privilege Escalation Vulnerability

iDefense Security Advisory 02.07.07
Feb 07, 2007


The Trend Micro AntiVirus scan engine is widely relied upon to provide
AntiVirus capabilities to desktop, server, and gateway systems. The engine
is licensed to several of Trend Micro's OEM partners. More information is
available on Trend Micro's web site at the following URL.


Local exploitation of an input validation vulnerability within version of TmComm.sys as included with Trend Micro's AntiVirus engine
could allow an attacker execute arbitrary code in kernel context.

This vulnerability specifically exists due to insecure permissions on the
\\.\TmComm DOS device interface. The permissions on this device allows
"Everyone" write access. This could allow a locally logged in user to
access functionality via IOCTLs which was designed for privileged use

Additionally, the IOCTL handlers for this DOS device interface do not
validate addresses passed to them. As such, it is possible to overwrite
arbitrary memory or execute attacker-supplied code in the context of the
kernel (RING 0).


Exploitation allows an attacker to elevate privileges by overwriting
arbitrary system memory or executing code within kernel context.


iDefense has confirmed the existence of this vulnerability in our
vulnerability lab. The configuration at verification time was as follows:

 * Trend Micro's PC-Cillin Internet Security 2007
 * TmComm.sys version
 * VsapiNI.sys (scan engine) version 3.320.0.1003

All products using Trend Micro's scan engine should be considered


Removing write permissions for "Everyone" appears to prevent access to the
vulnerable code. iDefense confirmed that the virus scanning engine was
still able to detect viruses. Although no side effects were witnessed in
Lab tests, normal functionality may be hindered.


"To address this vulnerability, Trend Micro recommends to customers to
update their Anti-Rootkit Common Module to version 1.600-1052.

Products that are set to Automatic Update will be updated immediately.

Manual Updating can also be performed by using the product's "Update
Now" function."

More information is available in Trend Micro's knowledge base at the link
shown below.


A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.


01/17/2007  Initial vendor notification
01/19/2007  Initial vendor response
02/07/2007  Coordinated public disclosure


This vulnerability was reported to iDefense by Ruben Santamarta of

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Permission is granted for the redistribution of this alert electronically.
It may not be edited in any way without the express written consent of
iDefense. If you wish to reprint the whole or any part of this alert in
any other medium other than electronically, please e-mail for permission.

Disclaimer: The information in the advisory is believed to be accurate at
the time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on, this

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