TS-2026-001

Description: Arbitrary command execution with elevated privileges in tssentineld What happened? tssentineld is a launchd service that is installed in managed environments when the AlwaysOn.Enabled MDM policy is present on macOS. Its sole responsibility is to ensure that Tailscale.app is relaunched if terminated. As a launchd service, it runs as root. The implementation used an NSTask and /bin/sh -c sudo -u [username], using basic string template substitution for the username. An attacker with either direct access to the memory backing the username string or by setting the current username to a malicious value could use this to inject commands running with the same privileges as tssentineld. This vulnerability is fixed in Tailscale version 1.94.0 and newer. What was the impact? Malicious local users that can manipulate their username or manipulate memory of tssentineld can execute arbitrary commands as root. Who was affected? The macOS standalone variant from 1.84.0 to 1.92.3, when configured via MDM to enable the AlwaysOn.Enabled policy is affected. tssentineld is only activated on clients managed by MDM and employing the AlwaysOn.Enabled policy and requires admin permission to install and activate. Memory manipulation to inject a malicious command requires a separate vulnerability or existing root access. The user may, however, modify their username in such a way that tssentineld could execute arbitrary shell commands with elevated privileges. The macOS package available from the App Store does not support the installation of launchd daemons and is not affected. What do I need to do? If you are using the AlwaysOn.Enabled policy with standalone macOS clients, update to version 1.94.0 or newer.