What is the difference between the 390.x, 470.x, and 510.x releases of the Linux Nvidia driver?

We have Quadro M4000 which is currently running 390.129, but the newest driver available from Nvidia is 510.68.02? According to this link (NVIDIA Driver | endoflife.date), 390.x is Long Term Support Branch (supported for 3 years), 470.x is also Long Term Support Branch (supported for 3 years), and 510.x is Production Branch (supported for 1 year). The latest Nvidia CVEs for the linux driver (CVE‑2022‑21813
CVE‑2022‑21814 listed on the Nvidia security bulletin page) only 470.x and 510.x are affected. So version 390.x is not affected by the vulnerabilities?

The 390 series is the legacy branch for the GF1xx “Fermi” series of GPUs. The Quadro M4000 is still supported by the latest releases so you don’t need to use a legacy driver series for it. Please refer to Appendix A. Supported NVIDIA GPU Products for a list of which products are supported by which driver series.

So do you know why release 390.x is not affected by the CVEs?
CVE‑2022‑21813|NVIDIA GPU Display Driver for Linux contains a vulnerability in the kernel driver, where improper handling of insufficient permissions or privileges may allow an unprivileged local user limited write access to protected memory, which can lead to denial of service.
CVE‑2022‑21814|NVIDIA GPU Display Driver for Linux contains a vulnerability in the kernel driver package, where improper handling of insufficient permissions or privileges may allow an unprivileged local user limited write access to protected memory, which can lead to denial of service.|

I don’t know offhand whether it’s affected or not, sorry. In general I would recommend using a newer driver since the 390 series is specifically for legacy products and is nearly out of support.