Zyxel ATP/USG Buffer Overflow (4.605.36 Patch1) DoS/RCE
CVE-2023-33009 Published on May 24, 2023
A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX series firmware versions 4.60 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.60 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.60 through 5.36 Patch 1, VPN series firmware versions 4.60 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.60 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.
Known Exploited Vulnerability
This Zyxel Multiple Firewalls Buffer Overflow Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. Zyxel ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, VPN, and ZyWALL/USG firewalls contain a buffer overflow vulnerability in the notification function that could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and remote code execution on an affected device.
The following remediation steps are recommended / required by June 26, 2023: Apply updates per vendor instructions.
Vulnerability Analysis
CVE-2023-33009 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. This vulnerability is known to be actively exploited by threat actors in an automatable fashion. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Type
What is a Classic Buffer Overflow Vulnerability?
The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold, or when a program attempts to put data in a memory area outside of the boundaries of a buffer. The simplest type of error, and the most common cause of buffer overflows, is the "classic" case in which the program copies the buffer without restricting how much is copied. Other variants exist, but the existence of a classic overflow strongly suggests that the programmer is not considering even the most basic of security protections.
CVE-2023-33009 has been classified to as a Classic Buffer Overflow vulnerability or weakness.
Affected Versions
Zyxel ATP series firmware:- Version 4.60 through 5.36 Patch 1 is affected.
- Version 4.60 through 5.36 Patch 1 is affected.
- Version 4.60 through 5.36 Patch 1 is affected.
- Version 4.60 through 5.36 Patch 1 is affected.
- Version 4.60 through 5.36 Patch 1 is affected.
- Version 4.60 through 4.73 Patch 1 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.