The flaw, which was first uncovered in April, involved users receiving a malformed message via iMessage.
"Receiving this message will cause Springboard to crash and respawn repeatedly, causing the UI not to be displayed and the phone to stop responding to input," said Google.
"This condition survives a hard reset, and causes the phone to be unusable as soon as it is unlocked."
While Macs could also be affected by the exploit, users could simply relaunch the soagent and the issue would be fixed.
The exploit was reported to Apple, who patched it in their iOS 12.3 release.
iPhone users are encouraged to update their operating systems as soon as possible to protect themselves against this exploit.