Rustworkx supports one minor version release at a time both for bug and security fixes. For example, if the most recent release is 0.12.1 the 0.12.x release series is currently supported.
To report vulnerabilities you can privately report a potential security issue via the Github security vulnerabilities feature. This can be done here:
https://github.com/Qiskit/rustworkx/security/advisories
Please do not open a public issue about a potential security vulnerability.
You can find more details on the security vulnerability feature in the Github documentation here: