Samsung has recently pushed the December 2021 security patch to Galaxy Fold, Galaxy Z Flip, and Z Fold 2. The security patch is available via a firmware update and is now rolling to users in the US. However, only unlocked variants are getting the update right now.
Samsung Galaxy Z Flip is getting the December 2021 security update via F700U1UES4EUL1, while Galaxy Fold and the Galaxy Z Fold 2 are getting F900U1UES6FUL1 and F916U1UES2EUL3 respectively.
The December 2021 security patch is already available for a bunch of flagship Galaxy phones, including Galaxy Note20, S20, Galaxy Z Fold 3, Z Fold 2, S20 FE 5G. The update is also available for some of the mid-range Galaxy phones.
Meanwhile, Galaxy Fold, Z Flip, and Z Fold 2 users in the US can check for the update manually by navigating to Settings> Software update.