D-Link FINALLY slams shut ‘Joel’s backdoor’
Better late than never: D-Link has issued the promised patch that closes an administrative backdoor in its SOHO broadband routers.
The patch has now been issued here.
If an attacker set their browser user agent string to read xmlset_roodkcableoj28840ybtide, their D-Link router would obligingly drop them straight into the admin page without a login. Only turning off remote administration would protect the device.
An amusing and really obvious (except that Vulture South didn’t notice it either) aspect of the vulnerability is what happens if the secret string is reversed. As pointed out by Sophos at Paul Ducklin’s Naked Security blog, the string (ignoring the xmlset_ part) reads:
Edit by 04882 Joel Backdoor
In other words, in our opinion, someone dropped the backdoor into the device during development and forgot to remove it later. ®