NovumOS, a custom 32-bit OS written in Zig and x86 Assembly, contains a privilege escalation vulnerability in versions before 0.24. Specifically, Syscall 12 (JumpToUser) does not validate the entry point address provided from user-space registers, allowing any Ring 3 user-mode process to jump to kernel addresses and execute arbitrary code with Ring 0 privileges. This flaw violates proper privilege management (CWE-269) and input validation (CWE-20). The vulnerability has been addressed in version 0.24. If immediate patching is not possible, running the OS in single-user mode without Ring 3 and disabling user-mode processes is recommended to mitigate risk.

Exploitation of this vulnerability allows a local attacker to escalate privileges from user mode (Ring 3) to kernel mode (Ring 0), resulting in full system compromise. The attacker can execute arbitrary code with the highest privileges, potentially leading to complete control over the affected system. The CVSS v3.1 base score is 9.4, reflecting critical impact on confidentiality, integrity, and availability.

A fix for this vulnerability is available in NovumOS version 0.24. Users and administrators should upgrade to this version to fully remediate the issue. If upgrading immediately is not feasible, it is recommended to restrict syscall access by running the system in single-user mode without Ring 3 and disabling user-mode processes, operating only with the kernel shell. These mitigations reduce the attack surface until the official fix can be applied.