Remote code execution in Zyxel routers

Published: 2020-12-19

Risk	High
Patch available	YES
Number of vulnerabilities	1
CVE-ID	N/A
CWE-ID	CWE-20
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	EMG3525-T50B Hardware solutions / Routers for home users EMG5523-T50B Hardware solutions / Routers for home users EMG5723-T50K Hardware solutions / Routers for home users EMG6726-B10A Hardware solutions / Routers for home users EX3510-B0 Hardware solutions / Routers for home users EX5510-B0 Hardware solutions / Routers for home users VMG3625-T50B Hardware solutions / Routers for home users VMG3925-B10B/B10C Hardware solutions / Routers for home users VMG3927-B50A_B60A Hardware solutions / Routers for home users VMG3927-B50B Hardware solutions / Routers for home users VMG3927-T50K Hardware solutions / Routers for home users VMG4005-B50B Hardware solutions / Routers for home users VMG4927-B50A Hardware solutions / Routers for home users VMG8623-T50B Hardware solutions / Routers for home users VMG8825-B50A_B60A Hardware solutions / Routers for home users VMG8825-Bx0B Hardware solutions / Routers for home users VMG8825-T50K Hardware solutions / Routers for home users VMG8924-B10D Hardware solutions / Routers for home users XMG3927-B50A Hardware solutions / Routers for home users XMG8825-B50A Hardware solutions / Routers for home users VMG1312-T20B Hardware solutions / Routers for home users
Vendor

Security Bulletin

This security bulletin contains one high risk vulnerability.

1) Input validation error

EUVDB-ID: #VU49097

Risk: High

CVSSv3.1: 8.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: N/A

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to insufficient validation of user-supplied input when processing HTTP requests in zhttpd webserver. A remote attacker can send specially crafted HTTP request to the affected device and execute arbitrary code on the system.

Successful exploitation of the vulnerability will result in a complete compromise of the router.

Mitigation

Install updates from vendor's website.

Note, some of the firmware updates are scheduled to be released during 2021.

Vulnerable software versions

EMG3525-T50B: before V5.50(ABSL.0)b8

EMG5523-T50B: before V5.50(ABSL.0)b8

EMG5723-T50K: before V5.50(ABOM.5)C0

EMG6726-B10A: before V5.13 (ABNP.6).C0

EX3510-B0: before V5.17(ABUP.3)C0

EX5510-B0: before V5.15(ABQX.3)C0

VMG3625-T50B: before V5.50(ABPM.4)C0

VMG3925-B10B/B10C: before V5.13(AAVF.16)C0

VMG3927-B50A_B60A: before V5.15(ABMT.5)C0

VMG3927-B50B: before V5.13(ABLY.6)C0

VMG3927-T50K: before V5.50(ABOM.5)C0

VMG4005-B50B: before V5.13(ABRL.5)C0

VMG4927-B50A: before V5.13(ABLY.6)C0

VMG8623-T50B: before V5.50(ABPM.4)C0

VMG8825-B50A_B60A: before V5.15(ABMT.5)C0

VMG8825-Bx0B: before V5.15(ABNY.5)C0

VMG8825-T50K: before V5.50(ABOM.5)C0

VMG8924-B10D: before V5.13(ABGQ.6)C0

XMG3927-B50A: before V5.15(ABMT.5)C0

XMG8825-B50A: before V5.15(ABMT.5)C0

VMG1312-T20B: before V5.50(ABSB.3)C0

External links

http://www.zyxel.com/support/Zyxel-security-advisory-for-remote-code-execution-and-denial-of-service-vulnerabilities-of-CPE.shtml

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.