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CERT Coordination Center

HPUX kmmodreg allows arbitrary file overwriting via symlink redirection of temporary file

Vulnerability Note VU#127435

Original Release Date: 2001-07-31 | Last Revised: 2001-08-01


The kmmodreg program distributed with some HPUX versions creates two temporary files with predictable names. Due to insecure handling of these files, an intruder may use them to overwrite arbitrary files during system boot via a symbolic link attack.


The kmmodreg program distributed with some HPUX versions creates two files in /tmp: /tmp.kmmodreg_lock and /tmp/kmpath.tmp. The creat() call used in this program does not check for prior existence of either file.


By creating symbolic links named for either of the two temporary files, an intruder can overwrite any file in the system with data from kmmodreg. Since kmmodreg runs automatically during reboot, no separate invocation is required. The overwrite may cause a file corruption leading to denial of service, or, since the temporary files are created to allow modification by anyone (protected 666), this may be used to allow modification of system files leading to increased user privileges.


Apply vendor patches; see the Systems Affected section below.

Vendor Information


Hewlett Packard Affected

Notified:  May 04, 2001 Updated: August 01, 2001



Vendor Statement


The information in the following Security Bulletin should be acted upon
as soon as possible. Hewlett-Packard Company will not be liable for any
consequences to any customer resulting from customer's failure to fully
implement instructions in this Security Bulletin as soon as possible.

PROBLEM: The kmmodreg(1M) inappropriately handles files.

PLATFORM: HP9000 Series 700/800 running HP-UX releases 11.XX only.

DAMAGE: Potential increase in privilege.

SOLUTION: Install the appropriate patch for the HP-UX release:
11.11 PHCO_24147,
11.04 PHCO_24197,
11.00 PHCO_24112.

AVAILABILITY: The patches are available now.
I. Background
Hewlett-Packard Company has discovered that the /usr/sbin/kmmodreg
command incorrectly performs its functions, causing a serious
potential for a denial of service attack or an increase of
This command is executed automatically at every system reboot.

II. Recommended solution
Application of the appropriate patch selected from the list below
completely solves this problem.

For HP-UX releases:
11.11 PHCO_24147,
11.04 PHCO_24197,
11.00 PHCO_24112.

III. To subscribe to automatically receive future NEW HP Security
Bulletins from the HP IT Resource Center via electronic mail,
do the following:

Use your browser to get to the HP IT Resource Center page

Under the Maintenance and Support Menu (Electronic Support
Center), click on the "more..." link. Then -

Use the 'Login' tab at the left side of the screen to login
using your ID and password. Check with your system
administrator to see if you have an existing login or use
the "Register" button at the left to create a login. You
will need to login in order to gain access to many areas of
the ITRC. Remember to save the User ID assigned to you, and
your password.

Under the "Notifications" section (near the bottom of
the page), select "Support Information Digests".

To -subscribe- to future HP Security Bulletins or other
Technical Digests, click the check box (in the left column)
for the appropriate digest and then click the "Update
Subscriptions" button at the bottom of the page.


To -review- bulletins already released, select the link
(in the middle column) for the appropriate digest.

To -gain access- to the Security Patch Matrix, select
the link for "The Security Bulletins Archive". (near the
bottom of the page) Once in the archive the third link is
to the current Security Patch Matrix. Updated daily, this
matrix categorizes security patches by platform/OS release,
and by bulletin topic. Us our free Security Patch Check
to completely automate the process of reviewing the patch
matrix for 11.XX systems.

For information on the Security Patch Check tool, see:

The security patch matrix is also available via anonymous ftp:

On the "Support Information Digest Main" page:
click on the "HP Security Bulletin Archive".

IV. To report new security vulnerabilities, send email to

Please encrypt any exploit information using the security-alert
PGP key, available from your local key server, or by sending a
message with a -subject- (not body) of 'get key' (no quotes) to

Permission is granted for copying and circulating this Bulletin to
Hewlett-Packard (HP) customers (or the Internet community) for the
purpose of alerting them to problems, if and only if, the Bulletin
is not edited or changed in any way, is attributed to HP, and
provided such reproduction and/or distribution is performed for
non-commercial purposes.

Any other use of this information is prohibited. HP is not liable
for any misuse of this information by any third party.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

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This vulnerability was first reported by Graf Potozky.

This document was last updated by Tim Shimeall.

Other Information

CVE IDs: CVE-2001-1256
Severity Metric: 11.64
Date Public: 2001-06-04
Date First Published: 2001-07-31
Date Last Updated: 2001-08-01 16:17 UTC
Document Revision: 6

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