If your modem has updated to 6.03.01, you are likely running a mature, stable iteration of a major software architecture. This version is typically rolled out to address specific latency issues or security vulnerabilities discovered in earlier iterations (such as 6.00.00 or 6.01.00). It is often considered a "safe harbor" build—a version that manufacturers and ISPs push to the masses because it is proven to be reliable.
Firmware is not universal; 6.03.01 is tailored to specific hardware platforms. Based on release notes from major manufacturers (Netgear, ARRIS, Surfboard, and TP-Link), this firmware is most commonly found on: modem firmware 6.03.01