An improper authentication vulnerability in the authentication module of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firm…

published 2023-11-30 2 y ago modified 2026-06-17 4 mo ago also EUVD-2023-39167

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 58%
public exploits: 0; none known

An improper authentication vulnerability in the authentication module of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to obtain system information by sending a crafted URL to a vulnerable device.

Patch / fix

links 1

zyxel.com/global/en/support/security-advisories/zyxel-security-advis… advisory

Exploit prediction

0.87% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Zyxel NAS326 firmware
Zyxel NAS542 firmware

Classification

Weakness

CWE-287 Improper Authentication

References

zyxel.com /global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection
vendor-advisory, patch

Sources

CVE List CVE-2023-35137
NVD CVE-2023-35137

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary