High severity7.5NVD Advisory· Published Nov 28, 2023· Updated Jun 17, 2026

CVE-2023-4398

Description

An integer overflow vulnerability in the source code of the QuickSec IPSec toolkit used in the VPN feature of the Zyxel ATP series firmware versions 4.32 through 5.37, USG FLEX series firmware versions 4.50 through 5.37, USG FLEX 50(W) series firmware versions 4.16 through 5.37, USG20(W)-VPN series firmware versions 4.16 through 5.37, and VPN series firmware versions 4.30 through 5.37, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions on an affected device by sending a crafted IKE packet.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

Zyxel/Zld
cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:*
Range: >=4.32,<=5.37
Zyxel/ATP series firmwarellm-fuzzy
Range: 4.32 - 5.37
Zyxel/USG FLEX series firmwarellm-fuzzy
Range: 4.50 - 5.37
Zyxel/USG20(W)-VPN series firmwarellm-fuzzy
Range: 4.16 - 5.37
Zyxel/VPN series firmwarellm-fuzzy
Range: 4.30 - 5.37
Zyxel/ATP seriescpe-rescue
Range: versions 4.32 through 5.37
Zyxel/USG FLEX seriescpe-rescue2 versions
versions 4.50 through 5.37+ 1 more
- (no CPE)range: versions 4.50 through 5.37
- (no CPE)range: versions 4.16 through 5.37
Zyxel/USG20(W)-VPN seriescpe-rescue
Range: versions 4.16 through 5.37
Zyxel/VPN seriescpe-rescue
Range: versions 4.30 through 5.37

Patches

Vulnerability mechanics

References

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-apsnvdVendor Advisory

News mentions

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cvss	0.488
epss	0.001
exploit	0.000
kev	0.000
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ransomware	0.000