Assuming that you have information in your ram that would identify who you are, and you are using the Tor browser but your pc is running a vulnerable version of openssl, could your memory be dumped by visiting a malicious site? Or does the TBB use it's own ssl tools rather than what you have installed on your system?
No, not with TBB.
TBB is based on Firefox ESR which doesn't use OpenSSL but NSS to do SSL/TLS.
Other software that uses a vulnerable Version of OpenSSL could be exploited by a malicious server.