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Vulnerability Note VU#426273

KTH Kerberos filesystem race condition on tickets stored in /tmp

Overview

There may be a race condition during the creation of Kerberos ticket files in the /tmp directory. This race condition may allow intruders with local access to the system to gain root privileges.

I. Description

During the creation of ticket files in the /tmp directory, a sequence of calls occur which may allow a local attacker to replace the ticket file with a symbolic link. If this symbolic link is followed when the ownership of the ticket file is set, the attacker may be able to gain ownership of files initially owned by root.

II. Impact

On systems where the sticky bit is not set on the /tmp directory, a local attacker can gain ownership of any file on the system. This allows the attacker to gain root privileges.

This attack may also be possible on systems where the /tmp directory does have its sticky bit set, depending on the exact sequence of calls used to create and set the ownership of the Kerberos ticket file.

III. Solution

Apply a patch from your vendor.

Systems Affected

VendorStatusDate Updated
AppleNot Vulnerable14-Dec-2000
BSDIUnknown14-Dec-2000
CalderaUnknown14-Dec-2000
Compaq Computer CorporationNot Vulnerable14-Dec-2000
Data GeneralUnknown14-Dec-2000
DebianUnknown14-Dec-2000
FreeBSDVulnerable14-Dec-2000
FujitsuNot Vulnerable11-Jan-2001
Hewlett PackardUnknown14-Dec-2000
IBMNot Vulnerable14-Dec-2000
KTH KerberosUnknown14-Dec-2000
MicrosoftNot Vulnerable14-Dec-2000
NetBSDUnknown14-Dec-2000
OpenBSDUnknown14-Dec-2000
RedHatUnknown14-Dec-2000
SGIUnknown14-Dec-2000
SonyUnknown14-Dec-2000
SunUnknown14-Dec-2000
Washington UniversityUnknown14-Dec-2000

References


http://www.securityfocus.com/bid/2093

Credit

Thanks to Jouko Pynnönen for reporting this vulnerability to the CERT/CC, and to Assar Westerlund for assisting in the development of this document.

This document was written by Cory F Cohen.

Other Information

Date Public12/09/2000
Date First Published12/19/2000 03:18:16 PM
Date Last Updated01/11/2001
CERT Advisory 
CVE Name 
Metric8.19
Document Revision9

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Copyright 2000 Carnegie Mellon University