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Home : Advisories : muh IRC bouncer remote vulnerability

Title: muh IRC bouncer remote vulnerability
Released by: FreeBSD
Date: 13th October 2000
Printable version: Click here


FreeBSD-SA-00:57                                           Security Advisory

                                                                FreeBSD, Inc.

Topic:          muh IRC bouncer remote vulnerability

Category:       ports

Module:         muh

Announced:      2000-10-13

Credits:        Maxime Henrion 

Affects:        Ports collection prior to the correction date.

Corrected:      2000-09-10 (4.1.1-RELEASE)

Vendor status:  Updated version released

FreeBSD only:   NO

I.   Background

muh is an IRC bouncer, a program that allows a host to act as a relay

between an IRC client on a local/remote machine and the IRC server.

II.  Problem Description

The muh port, versions 2.05c and before, contains a vulnerability

which allows remote users to gain the privileges of the user running

muh. This is accomplished by sending a carefully crafted exploit

string containing string format operators to a user using muh but who

is not connected. When the user reconnects and executes '/muh read',

muh will allow the remote attacker to execute arbitrary code as the

local user.

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

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

nearly 4000 third-party applications in a ready-to-install format.

The ports collections shipped with FreeBSD 3.5.1 and 4.1 contain this

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

corrected prior to the release of FreeBSD 4.1.1.

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

Remote IRC users can cause arbitrary code to be executed as the user

running muh.

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

system is not vulnerable to this problem.

IV.  Workaround

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

V.   Solution

One of the following:

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

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

correction date, obtained from:






NOTE: It may be several days before updated packages are available.

3) download a new port skeleton for the cvsweb 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: 2.6.2







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