The mount_smbfs utility is used to mount a remote SMB share locally. It is installed set-uid root, so as to allow unprivileged users to mount shares, and is present in a default installation on both the Server and Desktop versions of Mac OS X. For more information visit the following URL.
Local exploitation of a stack based buffer overflow vulnerability in Apple Inc.'s Mac OS X mount_smbfs utility could allow an attacker to execute arbitrary code with root privileges.
The vulnerability exists in a portion of code responsible for parsing command line arguments. When processing the -W option, which is used to specify a workgroup name, the option's argument is copied into a fixed sized stack buffer without any checks on its length. This leads to a trivially exploitable stack based buffer overflow.
Exploitation of this vulnerability results in the execution of arbitrary code with root privileges. In order to exploit this vulnerability, an attacker must have execute permission for the set-uid root mount_smbfs binary.
iDefense has confirmed the existence of this vulnerability in Mac OS X version 10.4.10, on both the Server and Desktop versions. Previous versions may also be affected.
Removing the set-uid bit from the mount_smbfs binary will prevent exploitation. However, non-root users will be unable to use the program.
Apple addressed this vulnerability within their Mac OS X 2007-009 security update. More information is available at the following URL.
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-3876 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.
07/16/2007 Initial vendor notification
07/17/2007 Initial vendor response
12/17/2007 Coordinated public disclosure
This vulnerability was discovered by Sean Larsson of VeriSign iDefense Labs.
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Copyright © 2007 Verisign, Inc.
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