CVE-2024-6343: zld Buffer Overflow — Fix

Description

A buffer overflow vulnerability in the CGI program of Zyxel ATP series firmware versions from V4.32 through V5.38, USG FLEX series firmware versions from V4.50 through V5.38, USG FLEX 50(W) series firmware versions from V4.16 through V5.38, and USG20(W)-VPN series firmware versions from V4.16 through V5.38 could allow an authenticated attacker with administrator privileges to cause denial of service (DoS) conditions by sending a crafted HTTP request to a vulnerable device.

Is your site exposed to CVE-2024-6343?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

4.9

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-120 CWE-120

Affected Products

Vendor	Product	Versions
zyxel	zld	4.32 — 5.39
zyxel	atp100	All
zyxel	atp100w	All
zyxel	atp200	All
zyxel	atp500	All
zyxel	atp700	All
zyxel	atp800	All
zyxel	zld	4.50 — 5.39
zyxel	usg_flex_100	All
zyxel	usg_flex_100ax	All
zyxel	usg_flex_100w	All
zyxel	usg_flex_200	All
zyxel	usg_flex_50	All
zyxel	usg_flex_500	All
zyxel	usg_flex_700	All
zyxel	zld	4.16 — 5.39
zyxel	usg_flex_50w	All
zyxel	zld	4.16 — 5.39
zyxel	usg_20w-vpn	All

References

Advisories & Patches

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-09-03-2024

Frequently Asked Questions

What is CVE-2024-6343? +

A buffer overflow vulnerability in the CGI program of Zyxel ATP series firmware versions from V4.32 through V5.38, USG FLEX series firmware versions from V4.50 through V5.38, USG FLEX 50(W) series firmware versions from V4.16 through V5.38, and USG20(W)-VPN series firmware versions from V4.16 through V5.38 could allow an authenticated attacker with administrator privileges to cause denial of service (DoS) conditions by sending a crafted HTTP request to a vulnerable device. It has a CVSS v3.1 base score of 4.9 (MEDIUM).

How severe is CVE-2024-6343? +

CVE-2024-6343 has a CVSS v3.1 score of 4.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2024-6343? +

CVE-2024-6343 affects products from zyxel, specifically: atp100, atp100w, atp200, atp500, atp700, atp800, usg_20w-vpn, usg_flex_100, usg_flex_100ax, usg_flex_100w, usg_flex_200, usg_flex_50, usg_flex_500, usg_flex_50w, usg_flex_700, zld. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-6343? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-27820

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain …

CVE-2025-11698

A denial-of-service issue exists in 5380/5480/5580 controllers boot firmware lower than version 1.072. This vulnerability could potentially allow a malicious …

CVE-2025-12012

A denial-of-service issue exists in 5380/5480/5580 controllers. This vulnerability could potentially allow a malicious user to write invalid file data …

CVE-2025-12011

A denial-of-service issue exists in 5370/5570 controllers. This vulnerability could potentially allow a remote user to load an invalid project, …

CVE-2024-13503

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in Newtec NTC2218, NTC2250, NTC2299 on Linux, PowerPC, ARM …

CVE-2024-6199

An unauthenticated attacker on the WAN interface, with the ability to intercept Dynamic DNS (DDNS) traffic between DDNS services and …

CVE-2024-6343