It was discovered that a systemd service that uses DynamicUser property can get new privileges through the execution of SUID binaries, which would allow to create binaries owned by the service transient group with the setgid bit set. A local attacker may use this flaw to access resources that will be owned by a potentially different service in the future, when the GID will be recycled.
This issue did not affect the versions of systemd as shipped with Red Hat Enterprise Linux 7 as they did not include support for DynamicUser property.
Created systemd tracking bugs for this issue:
Affects: fedora-all [bug 1703357]
Name: Jann Horn (Google Project Zero)