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.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Vpn100_firmware | Zyxel | 4.32 | 5.21 |