CVE-2019-15803: zyxel gs1900-10hp_firmware Improper Authentication

Vulnerability summary

CVE-2019-15803 is a critical (CVSS 9.1) Improper Authentication vulnerability in zyxel gs1900-10hp_firmware. EPSS estimates a 1.32% chance of exploitation in the next 30 days, higher than 70.4% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 14-11-2019
   PublishedVulnerability first disclosed.
2. 05-08-2024
   Last modifiedVulnerability information updated.

Description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Through an undocumented sequence of keypresses, undocumented functionality is triggered. A diagnostics shell is triggered via CTRL-ALT-t, which prompts for the password returned by fds_sys_passDebugPasswd_ret(). The firmware contains access control checks that determine if remote users are allowed to access this functionality. The function that performs this check (fds_sys_remoteDebugEnable_ret in libfds.so) always return TRUE with no actual checks performed. The diagnostics menu allows for reading/writing arbitrary registers and various other configuration parameters which are believed to be related to the network interface chips.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.