Vulnerability Note VU#570952

Redhat Linux diskcheck.pl creates predictable temporary file and fails to check for existing symbolic link of same name

Overview

Diskcheck.pl is a PERL script, part of Red Hat's powertools suite, that alerts a system administrator if any file system approaches capacity. In creating email alerts, diskcheck.pl creates insecure temporary files in a world-writable directory, which may permit an attacker to corrupt any writable file on the system.

I. Description

Diskcheck.pl is designed to run hourly. When any file system approaches capacity, it generates an email message to the system administrator, using a temporary file with a predictable name in the /tmp directory, without checking for the prior existence or ownership of this file. By its nature, Disckcheck runs with setuid root.

II. Impact

By creating a symbolic link with appropriate name and pointed to any writable file on the system, a local attacker can corrupt that file when diskcheck detects a file system approaching capacity.

III. Solution

Apply vendor patches; see the Systems Affected section below.

Modify diskcheck.pl to remove any file from /tmp named for its temporary file.

Systems Affected

Vendor	Status	Date Notified	Date Updated
RedHat	Vulnerable	4-Oct-2001

References

http://www.securityfocus.com/bid/2050
http://www.linuxsecurity.com/advisories/redhat_advisory-955.html

Credit

This vulnerability was first announced by Stan Bubrouski .

This document was last modified by Tim Shimeall.

Other Information

Date Public:	2000-12-20
Date First Published:	2001-10-08
Date Last Updated:	2001-10-08
CERT Advisory:
CVE-ID(s):	CAN-2000-0715
NVD-ID(s):	CAN-2000-0715
US-CERT Technical Alerts:
Metric:	4.32
Document Revision:	10

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