Is the used vulnerability closed after a jailbreak? If a vulnerability is used to jailbreak an iPhone or iPad, is that vulnerability typically closed/fixed as part of the jailbreak (itself, or a recommended next step) ?

In other words: if a new release of iOS fixes a security hole, then can the user have that hole fixed on his device while keeping an older version of iOS (jailbreaked)? Or is it a choice: either the pros of jailbreak (but with a known vulnerability) or no vulnerability (and newer iOS), but no jailbreak?
Jailbreaking doesn't immediately make older iOS immune to vulnerabilities with newer iOS, but it has been possible to install tweaks which protect against certain exploits.

These might not be the same implementations as with the newer iOS, but serve to protect against specific exploits. For example, SpectrePatch is a jailbreak tweak for older versions of iOS to protect against Spectre.

A survey of a broad range of security professionals would be iOS devices are less secure when jailbroken. 


https://www.tomsguide.com/us/iphone-jailbreak-risks,news-18850.html