Windows MRXSMB.SYS MRxSmbCscIoctlOpenForCopyChunk Overflow
iDefense Security Advisory 06.13.06 http://www.idefense.com/application/poi/display?type=vulnerabilities June 13, 2006
Microsoft Windows Operating System is system software for Intel based PCs. More information can be found at the vendor website:
Local exploitation of a buffer overflow vulnerability in Microsoft Corp.'s Windows Operating System could allow attackers to gain SYSTEM privileges.
The vulnerability specifically exists due to a logic error in the Microsoft Client Side Caching (CSCDLL.DLL) and Microsoft Server Message Block Redirector Driver (MRXSMB.SYS) code. The Microsoft Client Side Caching infrastructure provides the user-mode portion of the "offline files" subsystem, which allows interaction with network files while offline and preserves file system permissions. The Microsoft Server Message Block Redirector Driver is the kernel-mode file system driver that provides the network redirector functionality utilized by CSC.
MRXSMB.SYS functions are exposed via IOCTL commands. An access validation error exists in the MrxSmbCscIoctlOpenForCopyChunk() function. In order to establish communication with the MRXSMB subsystem, a file handle to a shadow device is created and DeviceIoControl() is used to issue commands. If an attacker utilizes the METHOD_NEITHER method flag, the address will be unchecked and an overwrite of kernel memory can occur resulting in ring0 code execution.
Successful exploitation of this vulnerability could result in elevation to SYSTEM privileges.
iDefense has confirmed the existence of this vulnerability in Microsoft Windows XP SP2. It is suspected that all versions of Microsoft Windows are vulnerable.
iDefense is unaware of any effective workaround for this issue.
VI. VENDOR RESPONSE
The vendor security advisory and appropriate patches are available at:
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2006-2373 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.
VIII. DISCLOSURE TIMELINE
12/09/2005 Initial vendor notification 12/13/2005 Initial vendor response 06/13/2006 Coordinated public disclosure
iDefense credits Rubén Santamarta with the discovery of this vulnerability.
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X. LEGAL NOTICES
Copyright © 2006 iDefense, Inc.
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