Welcome to the Forum.  Thanks for your question although in the spirit of full disclosure, I must tell you that "theoretical" questions have little value.  Theoretically you could be struck by a meteorite falling from space while reading this. That does not make it a realistic concern.  If yo have a concern, say so.---

Thank you Dr. Hook.

 

Hands are typically not an infection site for STIs provided a potentially infected person has a lesion/cut on them, correct (with the exception of syphilis maybe but rarely)?

 

However, and I suppose I am really overthinking this – if there is fresh infected blood flow to the hands while bleeding assuming that is happening at the time of masturbation and hypothetically the infected material in the blood directly connects with the mucosal surface of the urethra of the recipient in masturbation - is there an apparent scientific explanation with regards to the viability of STI pathogens considering their fragility, irrespective of viral load, why the recipient wouldn’t become infected practically speaking?

 

I essentially feel vulnerable if mucosal surface is exposed.

Correct, STIs are not transferred to or from hands.  Cuts and abrasions do not change this generalization.  The FACT is that transfer of the sort you describe has not been observed- quite the contrary. Blood and secretions on hands do NOT result in infection.  The mucosal surface is not that easy to access, exposure to the environment eliminates the infectiousness of any pathogen present and the amount of material (and organisms) transferred is mechanically reduced with each transfer.  These reasons combine to provide a logical scientific reason why transfer of fluids or blood in the process of masturbation does not lead to infection and is classified as safe sex by virtually every authority on the subject.  You are overthinking this!  EWH .---

Final thought – this is probably overthinking at its best, although I am having trouble ignoring it:

 

What about infected blood not (or minimally) exposed to the environment if just exiting the cut when the hand/finger(s) directly contact the urethra inside the penis during masturbation?

 

Is that the theoretical risk - potentially transmittable with sufficient viral load?

Thanks Dr. Hook

You are definitely overthinking this.---