A downgrade from two-factor authentication to one-factor authentication vulnerability in the CGI program of Zyxel USG/ZyWALL series firmwar…

published 2022-05-24 4y ago modified 2026-06-17 4mo ago also EUVD-2022-15940

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits: 0; none known

A downgrade from two-factor authentication to one-factor authentication vulnerability in the CGI program of Zyxel USG/ZyWALL series firmware versions 4.32 through 4.71, USG FLEX series firmware versions 4.50 through 5.21, ATP series firmware versions 4.32 through 5.21, and VPN series firmware versions 4.32 through 5.21, that could allow an authenticated attacker to bypass the second authentication phase to connect the IPsec VPN server even though the two-factor authentication (2FA) was enabled.

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Exploit prediction

0.74% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	4.0	AV:N/AC:L/Au:S/C:N/I:P/A:N

Affected products

Zyxel USG/ZyWALL series firmware
Zyxel USG FLEX series firmware
Zyxel ATP series firmware
Zyxel VPN series firmware

Classification

Weakness

CWE-287 Improper Authentication

References

zyxel.com /support/multiple-vulnerabilities-of-firewalls-AP-controllers-and-APs.shtml
vendor-advisory

Sources

CVE List CVE-2022-0910
NVD CVE-2022-0910

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