3-Year-Old RCE Bug Puts Millions Of OpenWRT Devices At Risk

OpenWRT is one of the most popular open-source operating systems powering millions of routers and other devices all over the world. A security researcher has found a critical RCE flaw in OpenWRT making a plethora of devices vulnerable to hacking.

The flaw, discovered by Guido Vranken from ForAllSecure, exists in the OPKG Package manager which is used for installing or updating updates in OpenWRT. The bug is tagged as CVE-2020-7982.

The Flaw

Vranken found that for three years, OpenWRT updates and installation files were pushed over unencrypted and insecure HTTP connections. This could allow an ill-intended hacker to deliver modified updates by bypassing the digital signature, applied before installation.

The bug initiates when the installation process of a received update begins. During the process, Vranken discovered that the SHA256Sum field, which is used for verifying the integrity of the update against SHA-256 hash, is not read correctly. The error arises due to a simple programming error.

If a hacker manages to create a file that matches the value of checksum, he can push a malicious update instead of the intended, untampered update file.

Not Easy To Exploit

Vranken mentions it’s not easy to exploit the flaw as it requires a hacker to execute a man-in-the-middle attack or fiddle around with the DNS server, the device is using. This means that a device using a secure DNS server and trusted users on the network aren’t susceptible to the flaw.

However, Vranken has not ruled out the possibility of ARP Cache poisoning and packet spoofing for exploiting the bug as he hasn’t tested either of the methods.

Patch issued, update now!

OpenWRT has issued versions 18.06.7 and 19.07.1 with the fix for the RCE flaw. If you have not updated your router or any other device running on OpenWRT, we recommend you update it as soon as possible to evade any potential attack.