Firmware Flaw Allows Attackers to Evade Security on Some Home Routers

Wired and wireless routers used by "millions" of home and small-business users are vulnerable to a firmware attack that can downgrade the devices to a less secure version that then allows the devices to be further compromised, cybersecurity firm NanoLock Security announced on Monday.

While few details of the vulnerability have been released by the company, NanoLock claims that the issue affects devices sold by Japanese networking and storage firm Buffalo and its US subsidiary Buffalo Americas, as well as "many other similar routers." NanoLock researchers met with Buffalo engineers in 2019 and described the attack, but the router manufacturer has not yet released an update, NanoLock said in an advisory.

The company decided to disclose the vulnerabilities because millions are potentially at risk, and Buffalo has not committed to issuing an update for the issue, says Yoni Kahana, vice president of business development for NanoLock Security.

"Unfortunately, at this time, users cannot do anything to protect themselves, and the Buffalo routers — as well as millions of others with this similar vulnerability — remain unsecure," he says. "The only thing that can reduce the risk of attack is to ensure that if they upgrade their router, it is with a higher version."

Home and small-business routers have become a common target for attackers. In 2016, hackers took control of hundreds of thousands of Internet-connected devices — many of them digital video cameras, but also routers — using the Mirai attack tool to compromise the devices, spread further, and level a reported 1-Tbps distributed denial-of-service (DDoS) attack against several targets.

Since then, a number of other attacks have targeted routers and Internet-connected devices, such as a brute-force credential-stuffing attack against Linksys routers and a series of attacks against virtual private network (VPN) appliances. In addition, researchers have focused on home routers, finding, for example, almost a dozen vulnerabilities in the networking stack of a common connect-device operating system.

These routers have become even more important to businesses as many employees continue to work from home, NanoLock stated in its advisory.

"With millions of people working from home in the throes of COVID-19, this exposes even more businesses than those who are already using a Buffalo router," Kahana says. "Hackers can take advantage of this vulnerability to take over residential routers where people are working from home and then use that as an entryway to infiltrate businesses' networks."

The current security issue arises from a weakness in the firmware update mechanism — the routers allow attackers to downgrade the firmware to a previous version, and since at least one previous version allows telnet access, the routers are vulnerable to attack, the company says.

"In 2019, NanoLock met with Buffalo's R&D team to demonstrate the hack on their router, exposing how hackers use web admin to downgrade the router from the secured version, v2.46, to v2.34 and then use telnet access to hack the firmware," the company said in its advisory. "This hack is particularly volatile, as the v2.46 contains a security patch that is supposed to address the vulnerabilities present in v2.34."

The company argued that disclosing the issue is in the interest of digital security. The vulnerability could "be a way to plant a zero-day attack code," Kahana says. "NanoLock is revealing this hack today to further emphasize to the infosec community that routers are vulnerable and that there are potentially millions at risk."

Such attacks indicate that router security needs to be hardened against unforeseen future vulnerabilities, the company said.

"To protect against hackers, router manufacturers need to take a different approach to cybersecurity, focusing on ways to address security vulnerabilities before they are exposed to ensure that their growing networks of routers will remain resilient in the face of attempted hacks," says Kahana.

Buffalo did not return a request for comment sent earlier in the day. 

Related Content:

Learn from industry experts in a setting that is conducive to interaction and conversation about how to prepare for that "really bad day" in cybersecurity. Click for more information and to register for this On-Demand event.