I’ve been an executor 3 times now and have 2 more very old relatives that have asked me to handle their estates. So you could say I have some experience.

My parents had stocks CD and all I had to do was sell them and withdraw the cash from their brokerage account. The key is they had a brokerage account in their name so as long as I had access to the account I could get easily sell all their stocks.

Once in cash I had to prove to the firm I was the authorized representative before I could close the account and access the funds.

If those shares are just in certificate form in a safe deposit box you could still deposit them in a brokerage account if they had one.

Working through shareholder services to change names on a certificate would likely take a long time.

If your parents are still alive but near death it may be wise for their executor to be added as a signer on their bank and brokerage accounts so they can easily access and move money. I did that with my parents and it made all the difference.

The harder part of being an executor is all the tax stuff. It took 2 more years before I was able to finally shut down all my parents affairs and file a final return. That was not fun.