There is an industry-standard definition of ‘perpetual’ licence. A licence is granted to use the software in perpetuity, but does not include a commitment to keep the software updated in perpetuity.
as time goes on, the viability of unsupported software continuing to work correctly diminishes, as hardware and operating systems evolve. It is a risk relying on unsupported software, and really limits ability to change underlying hardware / OS, since any change may cause the software to not work on that newer infrastructure.
in this case, the op took that risk and lost. However, the supplier should make the patch available - although the late news that the patch was available for 3 years, 2017-2019, does change things from a reasonableness perspective.
again, a perpetual licence does not mean it is supported perpetually. By the way, licences software is not owned by the licencee, ownership remains with the licencor.
i don’t think the op will get an outcome here at no cost - I would say he’s going to have to acquire new software - that’s my prediction.