A format string vulnerability in Zyxel ATP series firmware versions from 4.32 up to and including 5.37 Patch 1, USG FLEX series firmware versions from 4.50 up to and including 5.37 Patch 1, USG FLEX 50(W) series firmware versions from 4.16 up to and including 5.37 Patch 1, USG20(W)-VPN series firmware versions from 4.16 up to and including 5.37 Patch 1, and USG FLEX H series firmware versions from 1.10 up to and including 1.10 Patch 1 could allow an authenticated IPSec VPN user to cause DoS conditions against the “deviceid” daemon by sending a crafted hostname to an affected device if it has the “Device Insight” feature enabled.