Debian: ISDNUtils Critical Exploit for Xmonisdn Security Risk

Xmonisdn is an X applet that shows the status of the ISDN links. You can
configure it to run two scripts when the left or right mouse button are
clicked on it. Xmonisdn was installed setuid root so that the scripts
could do things like add and delete the default route. However is that
while the scripts were checked for owner root and not writeable by group
or others the scripts are run via the system() library function, which
spawns a shell to run it. This means that the scripts are open to attack
via IFS and/or PATH manipulation.

However, the setuid root isn't necessary anymore as the ISDN system now
offers other ways of preventing dialouts besides by manipulating network
routes. This can be done by anyone who can access /dev/isdnctrl0 and
/dev/isdninfo. On debian systems those are rw for group dialout, so if
xmonisdn is run by someone in group dialout, they can execute the
necessary isdnctrl commands.

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dpkg -i file.deb
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