From external source, Tim Allison:

I haven't seen any blog posts about this particular issue, and it seems like the regex engine should do something smarter. This is not the well known backtracking reDos thing or the well known stackoverflow kind of thing.
The trigger is a numeric quantifier operator attached to basically nothing.
I may be using the wrong terms.
an example {04184633}278-]4^6665]7
This comes from fuzzing...

Our reproducer:
jshell> time(() -> Pattern.compile("{1}3234512234").matcher("123".repeat(100)).find())
0s

jshell> time(() -> Pattern.compile("{12}3234512234").matcher("123".repeat(100)).find())
0s

jshell> time(() -> Pattern.compile("{123}3234512234").matcher("123".repeat(100)).find())
0s

jshell> time(() -> Pattern.compile("{1234}3234512234").matcher("123".repeat(100)).find())
0s

jshell> time(() -> Pattern.compile("{12345}3234512234").matcher("123".repeat(100)).find())
0.0009993s

jshell> time(() -> Pattern.compile("{123456}3234512234").matcher("123".repeat(100)).find())
0.0040019s

jshell> time(() -> Pattern.compile("{1234567}3234512234").matcher("123".repeat(100)).find())
0.0320831s

jshell> time(() -> Pattern.compile("{12345678}3234512234").matcher("123".repeat(100)).find())
0.3749385s

jshell> time(() -> Pattern.compile("{123456789}3234512234").matcher("123".repeat(100)).find())
3.9860775s

jshell> time(() -> Pattern.compile("{1234567890}3234512234").matcher("123".repeat(100)).find())
38.638369s

With time() defined as:
       void time(Runnable runnable) {
           var start = java.time.Instant.now();
           runnable.run();
           var duration = java.time.Duration.between(start, java.time.Instant.now());
           System.out.println(duration.toString().substring(2).replaceAll("(\\d[HMS])(?!$)", "$1 ").toLowerCase());
       }