D-Link published patches on Monday for a firmware coding goof that could allow attackers to remotely change the settings of several of its router models.
Craig Heffner, a vulnerability researcher who specializes in wireless and embedded systems, wrote on Oct. 12 that the web interface for some D-Link routers could be accessed remotely by setting a browser’s user agent string to “xmlset_roodkcableoj28840ybtide.”
The string suggests a backdoor was intentionally inserted into the firmware. Read in reverse, the value reads in part “edit by 04882 joel backdoor.”
The patches are for D-Link router models DIR-100, DIR-120, DI-524, DI-524UP, DI-604UP, DI-604+, DI-624S and the TM-G5240. Some devices made by Planex and Alpha Networks may also be vulnerable, D-Link said, presumably because they use the same firmware.
The flaw can be exploited if the routers have a remote management feature enabled. Remote management is disabled by default on all routers, D-Link said, but is included for “customer care troubleshooting.”
The vulnerability, contained in the firmware shipped with the routers, could be used to change settings and steal information.
After the flaw was discovered, D-Link said it would publish fixes by the end of October. It was unclear from its advisory what caused the delay.
Heffner wrote that the problem may have been discovered long ago by someone else. He found the particular user agent string that unlocks the Web interface on a Russian forum three years ago.