[ advisories | exploits | discussions | news | conventions | security tools | texts & papers ]
 main menu
- feedback
- advertising
- privacy
- FightAIDS
- newsletter
- news
- read forum
- new topic
- search

- meetings list
- recent additions
- add your info
 top 100 sites
- visit top sites
- sign up now
- members

- add your url
- add domain
- search box
- link to us

- our projects
- free email
 m4d network
- security software
- secureroot
- m4d.com
Home : Advisories : mgetty can create or overwrite files

Title: mgetty can create or overwrite files
Released by: FreeBSD
Date: 20th November 2000
Printable version: Click here


FreeBSD-SA-00:71                                           Security Advisory

                                                                FreeBSD, Inc.

Topic:          mgetty can create or overwrite files

Category:       ports

Module:         mgetty

Announced:      2000-11-20

Credits:        Stan Bubrouski 

Affects:        Ports collection prior to the correction date.

Corrected:      2000-9-10

Vendor status:  Updated version released

FreeBSD only:   NO

I.   Background

mgetty is a replacement for the getty utility designed for use with

data and fax modems.

II.  Problem Description

The mgetty port, versions prior to, contains a

vulnerability that may allow local users to create or overwrite any

file on the system.  This is due to the faxrunqd daemon (which usually

runs as root) following symbolic links when creating a .last_run file

in the world-writable /var/spool/fax/outgoing/ directory.

This presents a denial of service attack since the attacker can cause

critical system files to be overwritten, but it is not believed the

attacker has the ability to control the contents of the overwritten

file.  Therefore the possibility of using this attack to elevate

privileges is believed to be minimal.

The mgetty port is not installed by default, nor is it "part of

FreeBSD" as such: it is part of the FreeBSD ports collection, which

contains over 4100 third-party applications in a ready-to-install

format.  The ports collections shipped with FreeBSD 3.5.1 and 4.1.1

contain this problem since it was discovered after the releases, but

it was corrected prior to the release of FreeBSD 4.2.

FreeBSD makes no claim about the security of these third-party

applications, although an effort is underway to provide a security

audit of the most security-critical ports.

III. Impact

Unprivileged local users may create or overwrite any file on the


If you have not chosen to install the mgetty port/package, then your

system is not vulnerable to this problem.

IV.  Workaround

Deinstall the mgetty port/package, if you you have installed it.

V.   Solution

One of the following:

1) Upgrade your entire ports collection and rebuild the mgetty port.

2) Deinstall the old package and install a new package dated after the

correction date, obtained from:






3) download a new port skeleton for the mgetty port from:


and use it to rebuild the port.

4) Use the portcheckout utility to automate option (3) above. The

portcheckout port is available in /usr/ports/devel/portcheckout or the

package can be obtained from:







Version: GnuPG v1.0.4 (FreeBSD)

Comment: For info see http://www.gnupg.org







(C) 1999-2000 All rights reserved.