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Multiple Vendor Kerberos kadmind Buffer Overflow Vulnerability

04.03.07

BACKGROUND

Kerberos is a network authentication protocol. It is used in client-server systems to provide user authentication by using a ticket based system. kadmind is the Kerberos administration server. It is used to configure principals and policies on the Kerberos. More information can be found on the vendor's website at the following URL.

http://web.mit.edu/Kerberos/

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in the Kerberos kadmind server, as included in various vendors' operating system distributions, could allow attackers to execute arbitrary code on a targeted host.

The vulnerability exists within the server's logging function, klog_vsyslog(). A call is made to vsprintf(), with the destination buffer passed as a fixed size stack buffer. User input is not properly validated before being passed to this function, and a stack based buffer overflow can occur.

ANALYSIS

Exploitation allows an attacker to execute arbitrary code with root privileges on the targeted host.

In order to exploit this vulnerability, an attacker must have valid credentials stored on the server. Administrator privileges are not necessary. The kadmind server runs on the master Kerberos server. Since the master server holds the KDC principal and policy database, a compromise could lead to a compromise of multiple hosts that use the server for authentication.

DETECTION

iDefense has confirmed the existence of this vulnerability with Kerberos version 1.5.1 on Fedora CORE 5. It is likely that all distributions that contain this version of Kerberos are vulnerable.

WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

VENDOR RESPONSE

The MIT Kerberos team has made patches available to address this vulnerability. For more information consult their advisory at the following URL.

http://web.mit.edu/Kerberos/advisories/MITKRB5-SA-2007-002-syslog.txt

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-0957 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

02/08/2007 Initial vendor notification
02/08/2007 Initial vendor response
04/03/2007 Coordinated public disclosure

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

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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 information.