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Samba SAMR Change Password Remote Command Injection Vulnerability
iDefense Security Advisory 05.14.07
http://labs.idefense.com/intelligence/vulnerabilities/ May 14, 2007
I. BACKGROUND Samba is a Unix server application used to implement Windows file sharing and domain controlling functionality. SAMR is the named pipe used to access the SAM, security accounts manager, database. This database stores login credentials on NT based systems. More information can be found at the following URL.
II. DESCRIPTION Remote exploitation of a command injection vulnerability within Samba Project's Samba could allow an attacker to execute arbitrary code with nobody privileges.
The vulnerability exists within the code responsible for updating a user's password in the SAM database. Unfiltered user input is passed to "/bin/sh". This allows an attacker to execute arbitrary shell commands with the privileges of the nobody user.
III. ANALYSIS Successful exploitation of this vulnerability allows an attacker to run arbitrary shell commands with the privileges of the nobody user.
An important mitigating factor is that this vulnerability occurs within a non-default configuration of Samba. Specifically, the 'username map script' option must be defined in the smb.conf file.
Valid credentials are not needed to exploit this vulnerability. In order to successfully change a password, it is necessary to provide the original password. However, the vulnerability can still be triggered regardless of whether or not the change password attempt fails.
IV. DETECTION iDefense has confirmed the existence of this vulnerability in Samba version 3.0.24. Previous versions of Samba release 3 may be vulnerable. Release version 2 and below did not have this feature.
V. WORKAROUND Removing the 'username map script' option from the smb.conf file will prevent this vulnerability from being triggered.
VI. VENDOR RESPONSE Samba has released version 3.0.25 as well as a patch for version 3.0.24 to address this issue. More information can be found in their announcement at the following URL.
VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-2447 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 05/07/2007 Initial vendor notification 05/07/2007 Initial vendor response 05/14/2007 Coordinated public disclosure
IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous.
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