Zyxel ATP/USG FLEX/USG FLEX 50(W)/USG20(W)-VPN path traversal

Summaryinfo

A vulnerability has been found in Zyxel ATP, USG FLEX, USG FLEX 50(W) and USG20(W)-VPN and classified as very critical. This affects an unknown function. The manipulation leads to path traversal. This vulnerability is referenced as CVE-2026-14818. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Zyxel ATP, USG FLEX, USG FLEX 50(W) and USG20(W)-VPN (the affected version unknown) and classified as very critical. This issue affects an unknown part. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

A path traversal vulnerability in the CLI command used to execute configuration files in Zyxel ATP series firmware versions from V4.32 through V5.42 Patch 1, USG FLEX series firmware versions from V4.50 through V5.42 Patch 1, USG FLEX 50(W) series firmware versions from V4.16 through V5.42 Patch 1, and USG20(W)-VPN series firmware versions from V4.16 through V5.42 Patch 1 could allow an authenticated attacker with administrator privileges to execute a crafted malicious configuration file on an affected device.

The advisory is shared at zyxel.com. The identification of this vulnerability is CVE-2026-14818 since 07/06/2026. The exploitation is known to be easy. The attack may be initiated remotely. The exploitation requires an enhanced level of successful authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/04/2026). MITRE ATT&CK project uses the attack technique T1006 for this issue.

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-2026-52569). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Network Encryption Software

Vendor

• Zyxel

Name

• ATP
• USG20(W)-VPN
• USG FLEX
• USG FLEX 50(W)

License

• commercial

Website

• Vendor: https://www.zyxel.com/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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