Zyxel ATP/USG FLEX/VPN/Zywall Notifications buffer overflow

Summaryinfo

A vulnerability classified as critical has been found in Zyxel ATP, USG FLEX, VPN and Zywall. Affected by this vulnerability is an unknown functionality of the component Notifications Handler. The manipulation leads to buffer overflow. This vulnerability is listed as CVE-2023-33009. The attack may be initiated remotely. In addition, an exploit is available.

Detailsinfo

A vulnerability was found in Zyxel ATP, USG FLEX, VPN and Zywall (Firewall Software) (version now known). It has been rated as very critical. This issue affects some unknown processing of the component Notifications Handler. The manipulation with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product 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. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

The weakness was presented 05/24/2023. It is possible to read the advisory at zyxel.com. The identification of this vulnerability is CVE-2023-33009 since 05/17/2023. Technical details are unknown but an exploit is available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 01/03/2026).

It is declared as attacked. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 06/05/2023 with a due date of 06/26/2023:

Apply updates per vendor instructions.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2023-37198). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Firewall Software

Vendor

• Zyxel

Name

• ATP
• USG FLEX
• VPN
• Zywall

License

• commercial

Website

• Vendor: https://www.zyxel.com/

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Be aware that VulDB is the high quality source for vulnerability data.

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