Description
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.
CVSS breakdown
CVSS 3.1
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Affected products
- Zyxel / ATP series firmware4.32 through 5.21 – 4.32 through 5.21
- Zyxel / USG FLEX series firmware4.50 through 5.21 – 4.50 through 5.21
- Zyxel / USG/ZyWALL series firmware4.32 through 4.71 – 4.32 through 4.71
- Zyxel / VPN series firmware4.32 through 5.21 – 4.32 through 5.21