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Zyxel Routers and Home WiFi Systems - Unprotected Root Access via UART Using Default Password

High
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Synopsis

On Zyxel models NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30, the UART port on the PCB board gives a root BusyBox shell that prompts for a non-user configurable hardcoded default password present in a configuration file on the firmware (/etc/uci_defconfig/system): 
/etc/uci_defconfig/system:
       option pwd "nbg6818@2019"
       option gui_pwd "1234"
       option language "en"
For this particular model (NBG6818), the default password is "nbg6818@2019". Other affected models will have different default passwords.

Solution

See vendor advisory for instructions on how to update to patched firmware.

Additional References

https://www.zyxel.com/support/Zyxel_security_advisory_for_pre-configured_password_management_vulnerability_of_home_routers_and_WiFi_systems.shtml

Disclosure Timeline

8/25/2021 - Vendor Alerted
8/25/2021 - Vendor Acknowledged
8/26/2021 - Vendor asked for more information
8/26/2021 - Tenable responded
8/30/2021 - Zyxel responds and plans to assigns CVE
9/3/2021 - Zyxel informs they plan to disclose on November 23
9/27/2021 - Zyxel asks for disclosure link information
10/5/2021 - Tenable responds with disclosure link information
11/23/2021 - Zyxel release patches

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Risk Information

CVE ID: CVE-2021-35033
Tenable Advisory ID: TRA-2022-06
Credit:
Nicholas Miles
CVSSv3 Base / Temporal Score:
7.8/7.0
CVSSv3 Vector:
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected Products:
NBG6818
NBG7815
WSQ20
WSQ50
WSQ60
WSR30
Risk Factor:
High
Additional Keywords:
zyxel
uart

Advisory Timeline

2/28/2022 - Advisory published
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