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Family: Red Hat Local Security Checks --> Category: infos

RHSA-2002-137: util Vulnerability Scan

Vulnerability Scan Summary
Check for the version of the util packages

Detailed Explanation for this Vulnerability Test

The util-linux package shipped with Red Hat Linux Advanced Server contains
a locally exploitable vulnerability.

The util-linux package contains a large variety of low-level system
utilities that are necessary for a Linux system to function. The 'chfn'
utility included in this package allows users to modify personal
information stored in the system-wide password file, /etc/passwd. In order
to modify this file, this application is installed setuid root.

Under certain conditions, a carefully crafted attack sequence can be
performed to exploit a complex file locking and modification race present
in this utility allowing changes to be made to /etc/passwd.

In order to successfully exploit the vulnerability and perform privilege
escalation there is a need for a minimal administrator interaction.
Additionally, the password file must be over 4 kilobytes, and the local
attackers entry must not be in the last 4 kilobytes of the password file.

The Common Vulnerabilities and Exposures project ( has
assigned the name CVE-2002-0638 to this issue.

An interim workaround is to remove setuid flags from /usr/bin/chfn and
/usr/bin/chsh. All users of Red Hat Linux should update to the errata
util-linux packages which contain a patch to correct this vulnerability.

Many thanks to Michal Zalewski of Bindview for alerting us to this issue.

Solution :
Threat Level: High

Click HERE for more information and discussions on this network vulnerability scan.


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