Vulnerabilities found in Zyxel Firewall Devices

Zyxel, a networking equipment manufacturer, recently discovered a critical security flaw in its firewall devices. Tracked as CVE-2023-28771, the vulnerability could be exploited to achieve remote code execution on affected systems.

In addition to this vulnerability, Zyxel has addressed several other high-severity flaws that could result in code execution and cause a denial-of-service (DoS) condition.

The most severe flaw among these is CVE-2022-43389, a buffer overflow vulnerability that affects 5G NR/4G LTE CPE devices. This vulnerability does not require authentication to exploit, leading to arbitrary code execution on the device. An attacker could access the device remotely and fully control its operation.

The company has also addressed a high-severity post-authentication command injection vulnerability affecting select firewall versions (CVE-2023-27991) that could permit an authenticated attacker to execute OS commands remotely. The affected devices include ATP, USG FLEX, USG FLEX 50(W)/USG20(W)-VPN, and VPN.

These vulnerabilities can be exploited to gain unauthorized access to Zyxel’s devices, allowing attackers to steal sensitive information, launch malware attacks, or cause widespread disruption to affected systems.

Acreto Solution

Acreto can effectively address both vulnerabilities for Zyxel devices. Especially Internet-touching devices such as firewalls and routers that can not be protected behind another device.

To Address CVE-2022-43389 and CVE-2023-27991 an organization can utilize Ecosystems to Isolate individual or groups of systems on a shared network or entire networks, limiting access only to systems that need to interoperate together.

An organization could also make use of Isolated Data Flows. This can be used to limit access to specified sources and destinations between network protocols and ports, and application protocols, as well as application programs. This can prevent authenticated attackers from executing OS commands remotely on the affected devices.

Ecosystems

Ecosystems deliver a dedicated security infrastructure that can be deployed per application, use-case, project or third-party. An Ecosystem inherently limits access only to users, devices, systems and applications that need to interoperate together.

Ecosystems support any technology, on any network, anywhere in the world. These include computers, mobile devices, IoTs, Offices, Clouds, SaaS and Data Centers.

Ecosystems can be configured as:

Eliminate the Internet Attack Surface

Eliminates any and all access from the Internet while Ecosystem members can interoperate with authorized systems and applications.

Eliminate the Internal Attack Surface

Ecosystems can easily isolate individual or groups of systems on a shared network or entire networks, to limit access only to systems that need to interoperate together. This is done with

Isolated Data Flows

Isolated data flows can be defined between two Ecosystem members to limit access to specified sources and destinations, network protocols and ports, application protocols as well as application programs.

Encrypted Secure Scan

Secure Scan addresses a key weakness in many security tools today. 90%+ of all communications is encrypted, yet only 10% of organizations have the means to secure these communications. Encrypted Secure Scan decrypts, scans, and re-encrypts communications inline and in real-time.

Any malicious content embedded in the encrypted payload is blocked, otherwise the clean and validated communication is delivered to its final destination.

Controls

• User Authorizes access to the Ecosystem by a user’s identity, including MFA, as authenticated by the organizations’ Directory Services such as Active Directory or LDAP, as well as third-party Identity Service Providers such as Okta, Ping, Duo, and CloudJump among others.
• Device Specifies a unique identity to each device to validate that a specified device that does not rely on a user to operate – such as an autonomous application or IoT, is allowed to join the Ecosystem. 

Application Program

Threat Prevention

After verification of network protocol, port, application protocol and application program, a deep inspection is performed on all communications. The effectiveness of this method is amplified by inline Encrypted Secure Scan. Threat prevention capabilities utilize two key methods:

• Threat Signature: Identifies and mitigates known bad exploits, malware, botnets and ransomware.
• Zero-Day Behavioral Analysis: Looks for behavioral indications of threats based on how system functions react to the payload, immediately and over time.

 

Simplicity

• Acreto Ecosystems are very easy to provision and deploy. There are no hardware dependencies or associated logistics.
• Provisioning an Ecosystem takes 3-5 minutes. Simply provide a unique name to the Ecosystem then choose the bandwidth desired and within a few minutes your Ecosystem providing a dedicated security infrastructure is ready.
• Depending on your connection options for Ecosystem members, deployment can take between 10 minutes to a few hours.

 

Mechanism of Attack

• CVE-2022-43389 (CVSS score: 9.8): A buffer overflow vulnerability in the library of the web server in Zyxel NR7101 firmware prior to V1.15(ACCC.3)C0, which could allow an unauthenticated attacker to execute some OS commands or to cause denial-of-service (DoS) conditions on a vulnerable device.
• CVE-2023-27991 (CVSS score: 8.8): The post-authentication command injection vulnerability in the CLI command of Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow an authenticated attacker to execute some OS commands remotely.

For more details on CVEs, visit: CVE – CVE (mitre.org)

• Products impacted by the vulnerabilities are:
  • ATP (versions ZLD V4.60 to V5.35, patched in ZLD V5.36)
  • USG FLEX (versions ZLD V4.60 to V5.35, patched in ZLD V5.36)
  • VPN (versions ZLD V4.60 to V5.35, patched in ZLD V5.36), and
  • ZyWALL/USG (versions ZLD V4.60 to V4.73, patched in ZLD V4.73 Patch 1)

 

About Acreto

Acreto delivers full-stack cybersecurity without products, logistics or significant security expertise. It creates and consolidates the best of cybersecurity into a single plug-and-play platform with automated updates to stay ahead of threats. Acreto activates enterprise-grade security instantly, so organizations can run safely, easily, and without interruption.