CVE-2023-22915

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

1.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-04-24 17:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 05:36 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.1% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-04-24 17:15 UTC

Last modified

2026-06-17 05:36 UTC

Exploit probability

1.1% · EPSS, next 30 days

Weakness

CWE-120 · Classic buffer overflow

Record status

Modified

Affected

• Zyxel Usg Flex 100 Firmware ≤ 5.35
• Zyxel Usg Flex 100w Firmware ≤ 5.35
• Zyxel Usg Flex 200 Firmware ≤ 5.35
• Zyxel Usg Flex 50 Firmware ≤ 5.35
• Zyxel Usg Flex 50w Firmware ≤ 5.35
• Zyxel Usg Flex 500 Firmware ≤ 5.35
• Zyxel Usg Flex 700 Firmware ≤ 5.35
• Zyxel vpn100 Firmware ≤ 5.35

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-22915.md and follow it. Check whether this project is affected by CVE-2023-22915. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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