Tenda AC20 shadow hard-coded credentials

A security flaw has been discovered in Tenda AC20 16.03.08.12. Affected by this vulnerability is an unknown functionality of the file /etc_ro/shadow. The manipulation leads to hard-coded credentials. It is possible to launch the attack on the local host. The complexity of an attack is rather high. The exploitation appears to be difficult. The exploit has been disclosed to the public and may be used.