Tailscale version below 1.18.2 blocks ACLs with proto field

critical

configurationUpdated Feb 2, 2026(via Exa)

Sources

Syntax reference for the tailnet policy filetailscale.com

Technologies:

Tailscalesubject

How to detect:

Tailscale clients running versions earlier than v1.18.2 will fail and block access rules that include the `proto` field in ACL definitions. This causes complete access rule failure for affected clients.

Recommended action:

Before adding `proto` fields to ACL rules, verify all Tailscale clients in the tailnet are running v1.18.2 or later. Upgrade any clients below this version or remove the `proto` field from rules if upgrades are not possible.