Zyxel fixed firewall unauthenticated remote command injection issue

Zyxel addressed a critical flaw affecting Zyxel firewall devices that allows unauthenticated, remote attackers to gain arbitrary code execution.

Zyxel has moved to address a critical security vulnerability (CVE-2022-30525, CVSS score: 9.8) affecting Zyxel firewall devices that enables unauthenticated and remote attackers to gain arbitrary code execution as the “nobody” user.

The issue was discovered by Rapid7 which reported it on April 13.

Zyxel silently addressed the flaw by releasing security updates on April 28, 2022, Rapid7 pointed out that this choice leaves defenders in the dark and only advantage the attackers.

“The affected models are vulnerable to unauthenticated and remote command injection via the administrative HTTP interface. Commands are executed as the nobody user.” reads the report published by Rapid7.

Below is the list of vulnerable products and related patches:

Affected modelAffected firmware versionPatch availability

USG FLEX 100(W), 200, 500, 700	ZLD V5.00 through ZLD V5.21 Patch 1	ZLD V5.30
USG FLEX 50(W) / USG20(W)-VPN	ZLD V5.10 through ZLD V5.21 Patch 1	ZLD V5.30
ATP series	ZLD V5.10 through ZLD V5.21 Patch 1	ZLD V5.30
VPN series	ZLD V4.60 through ZLD V5.21 Patch 1	ZLD V5.30

According to Rapid 7, there are more than 15,000 internet-facing vulnerable systems tracked by the Shodan search engine. The researchers also developed a Metasploit module for this issue and published a video PoC of the attack:

“Apply the vendor patch as soon as possible. If possible, enable automatic firmware updates. Disable WAN access to the administrative web interface of the system.” concludes the report.

The vendor the following issues in its VMG3312-T20A wireless router and AP Configurator:

a command injection (CVE-2022-26413);a buffer overflow (CVE-2022-26414) a local privilege escalation (CVE-2022-0556) flaw.

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Pierluigi Paganini

(SecurityAffairs – hacking, Zyxel)