CVE-2023-34140 : What You Need to Know

A buffer overflow vulnerability in Zyxel products has been identified, potentially allowing denial of service attacks by sending a crafted request to the CAPWAP daemon.

Understanding CVE-2023-34140

This CVE-2023-34140 affects multiple Zyxel products due to a buffer overflow vulnerability, posing a risk of denial of service attacks if exploited.

What is CVE-2023-34140?

CVE-2023-34140 is a buffer overflow vulnerability in Zyxel ATP series, USG FLEX series, USG FLEX 50(W) series, USG20(W)-VPN series, VPN series, NXC2500, and NXC5500 firmware versions. It could allow an unauthenticated LAN-based attacker to cause denial of service (DoS) conditions by leveraging the vulnerability in the CAPWAP daemon.

The Impact of CVE-2023-34140

The impact of this vulnerability is significant as it could be exploited by attackers to disrupt services and cause downtime by sending malicious requests.

Technical Details of CVE-2023-34140

The vulnerability is classified under CWE-120 - Buffer Copy without Checking Size of Input, also known as 'Classic Buffer Overflow'.

Vulnerability Description

The buffer overflow vulnerability in Zyxel firmware versions mentioned allows an unauthenticated LAN-based attacker to trigger denial of service conditions by sending a specifically crafted request to the CAPWAP daemon.

Affected Systems and Versions

ATP series firmware: 4.32 through 5.36 Patch 2
USG FLEX series firmware: 4.50 through 5.36 Patch 2
USG FLEX 50(W) series firmware: 4.16 through 5.36 Patch 2
USG20(W)-VPN series firmware: 4.16 through 5.36 Patch 2
VPN series firmware: 4.30 through 5.36 Patch 2
NXC2500 firmware: 6.10(AAIG.0) through 6.10(AAIG.3)
NXC5500 firmware: 6.10(AAOS.0) through 6.10(AAOS.4)

Exploitation Mechanism

An unauthenticated LAN-based attacker could exploit the vulnerability by sending a maliciously crafted request to the CAPWAP daemon, potentially leading to denial of service conditions.

Mitigation and Prevention

To mitigate the risks associated with CVE-2023-34140, immediate steps should be taken along with implementing long-term security practices and applying necessary patches and updates.

Immediate Steps to Take

Organizations should restrict network access to the affected devices and services.
Network monitoring for suspicious activities should be enhanced.
Implementing firewall rules and intrusion detection systems can help in detecting and blocking malicious traffic.

Long-Term Security Practices

Regular security assessments and audits should be conducted to identify and address vulnerabilities proactively.
Ensuring all systems are up to date with the latest security patches and firmware updates.
Employee training on cybersecurity best practices and awareness about social engineering attacks.

Patching and Updates

Zyxel has released patches to address the vulnerability in the affected firmware versions. Organizations are advised to promptly apply these patches to secure their systems.