CVE-2023-4398 — An integer overflow vulnerability in the source code of the QuickSec IPSec toolk

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,

01What is this vulnerability?

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…

02Affected products

Vendor	Product	Versions
Zyxel	ATP series firmware	versions 4.32 through 5.37
Zyxel	USG FLEX series firmware	versions 4.50 through 5.37
Zyxel	USG FLEX 50(W) series firmware	versions 4.16 through 5.37
Zyxel	USG20(W)	VPN series firmware — versions 4.16 through 5.37
Zyxel	VPN series firmware	versions 4.30 through 5.37

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-11-28T01:48:28.586Z
• Last modified: 2024-10-17T17:38:37.172Z

09References

• www.zyxel.com — https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advis…