Cyber Resilience

CVE-2023-27990

Medium

Published: 24 April 2023

Published
24 April 2023
Modified
25 February 2026
KEV Added
Patch
CVSS Score v3.1 4.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0037 59.0th percentile
Risk Priority 10 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2023-27990 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Zyxel Atp200 Firmware. Its CVSS base score is 4.8 (Medium).

Operationally, ranked in the top 41.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

The cross-site scripting (XSS) vulnerability in Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35, and VPN series firmware…

more

versions 4.30 through 5.35, which could allow an authenticated attacker with administrator privileges to store malicious scripts in a vulnerable device. A successful XSS attack could then result in the stored malicious scripts being executed when the user visits the Logs page of the GUI on the device.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

zyxel
atp200 firmware
4.32 — 5.36
zyxel
atp100 firmware
4.32 — 5.36
zyxel
atp700 firmware
4.32 — 5.36
zyxel
atp500 firmware
4.32 — 5.36
zyxel
atp100w firmware
4.32 — 5.36
zyxel
atp800 firmware
4.32 — 5.36
zyxel
usg flex 100 firmware
4.50 — 5.36
zyxel
usg flex 50 firmware
4.50 — 5.36
zyxel
usg flex 200 firmware
4.50 — 5.36
zyxel
usg flex 500 firmware
4.50 — 5.36
+9 more product configuration(s) — see NVD for full list

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

References