Reports of new vulnerabilities pop up every now and then. An unchecked buffer in a piece of software could easily slip through code reviews and testing. If found and exploited, it could lead to total control over a computer or even network.
According to the following eEye report several D-Link routers can be attacked remotely, leading to total control of the router, and possibility to get into the network it protects.
http://www.eeye.com/html/research/advisories/AD20060714.html
Like I said, bugs like these are found every now and then in software and hardware devices (e.g. HP printers), but what is interesting here is that apparently D-Link has not bothered to fix it even though it was reported to them back in February! It tells you a bit how interested they seem to be to fix problems with their products.
Here is some more detailed information:
http://www.blackhat.com/presentations/bh-europe-06/bh-eu-06-Jack.pdf
Funny cat & dog pic on page 25 btw..