Raw vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-40317 is a critical-severity Improper Input Validation (CWE-20) vulnerability in Minecanton209 Novumos. Its CVSS base score is 9.3 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Abuse Elevation Control Mechanism (T1548); ranked at the 13th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-2 (Account Management) and AC-24 (Access Control Decisions) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-40317 affects NovumOS, a custom 32-bit operating system written in Zig and x86 Assembly, in versions prior to 0.24. The vulnerability resides in Syscall 12 (JumpToUser), which accepts an arbitrary entry point address from user-space registers without validation. This flaw enables any Ring 3 user-mode process to jump directly to kernel addresses, executing arbitrary code in Ring 0 kernel context and resulting in local privilege escalation. The issue is rated with a CVSS v3.1 base score of 9.3 (AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) and is associated with CWE-20 (Improper Input Validation) and CWE-269 (Improper Privilege Management).
Local attackers with access to a Ring 3 user-mode process can exploit this vulnerability without privileges or user interaction. By invoking Syscall 12 with a crafted kernel address in user-space registers, they achieve arbitrary code execution in kernel mode, granting full control over the system, including complete confidentiality, integrity, and availability impacts due to the scope change to unchanged components.
The NovumOS security advisory and release notes recommend updating to version 0.24, where the issue is fixed. As a temporary mitigation, if immediate updating is not possible, operators should restrict syscall access by running the system in single-user mode without Ring 3 support and disable all user-mode processes, limiting operations to the kernel shell only. Relevant resources include the GitHub release for v0.24 and the security advisory at GHSA-xjx3-gjh9-45fm.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-23630
Vulnerability Data
NovumOS is a custom 32-bit operating system written in Zig and x86 Assembly. In versions prior to 0.24, Syscall 12 (JumpToUser) accepts an arbitrary entry point address from user-space registers without validation, allowing any Ring 3 user-mode process to jump…
more
to kernel addresses and execute arbitrary code in Ring 0 context, resulting in local privilege escalation. This issue has been fixed in version 0.24. If developers are unable to immediately update, they should restrict syscall access by running the system in single-user mode without Ring 3, and disable user-mode processes by only running kernel shell with no user processes. This issue has been fixed in version 0.24.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 9 hardening rules · 6 OS baselines
—
Mitigating Controls (NIST 800-53 r5) AI
Account management directly governs assignment and tracking of privileges so proper implementation stops the weakness from being introduced.
Requiring explicit access-control decisions ensures privileges are evaluated rather than assumed or omitted.
Access enforcement applies the correct privilege checks at every request, structurally preventing unintended spheres of control.
Separation of duties constrains how privileges may be assigned, reducing the chance of overly broad actor control.
Least privilege is the direct countermeasure to improper privilege management; implementing it eliminates the root cause.
Developer testing and evaluation can discover missing input validation through analysis or test cases.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.AA-05 enforces least privilege/SoD and periodic reviews that directly remove most privilege-assignment defects, yet CWE-269 also covers escalation paths and role design outside a single access-management control.
PR.AA-01 supplies credential/identity lifecycle support that can reduce some privilege-assignment errors but does not itself assign, modify, or check privileges, leaving most of CWE-269's risk unaddressed.
Config baselines and default reviews can enforce some privilege-related settings (one facet) but do not address code-level assignment/tracking logic that defines CWE-269.
PR.PS-05 can partially limit exploitability of some privilege issues via execution restrictions, but does not address the core design/implementation flaws of CWE-269 at all.
Secure SDLC practices directly require and enforce input validation during development.
PR.DS-10 protects data-in-use without touching privilege assignment/tracking, so it neither prevents CWE-269 nor removes more than one narrow facet of its risk.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Explicit restrictions on privileged access and segregation of duties limit the scope of privileges that can be assigned, reducing the chance that excessive or unnecessary privileges are granted to entities.
Requiring owner approval, segregation of duties, and periodic reviews prevents the assignment of excessive or unnecessary privileges to users or processes.
Defining and communicating authorization levels for each role limits the assignment of excessive or unnecessary privileges.
Separating duties such as developing software from administering production systems prevents any one person from accumulating excessive privileges that would constitute improper privilege management.
Logging every use of privileges and protecting those records makes it harder for an attacker who has obtained elevated rights to operate without leaving evidence.
Defining and enforcing documented authorization levels for each utility program prevents the assignment of excessive privileges that would let an attacker abuse those utilities beyond their intended scope.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
RHEL 8 (1 rule)
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-20
Windows 10 (1 rule)
- V-220712 Only accounts responsible for the administration of a system must have Administrator rights on the system. prevents CWE-269
Windows Server 2016 (1 rule)
- V-225007 Only administrators responsible for the member server or standalone or nondomain-joined system must have Administrator rights on the system. prevents CWE-269
Windows Server 2019 (1 rule)
- V-205746 Windows Server 2019 must only allow Administrators responsible for the member server or standalone or nondomain-joined system to have Administrator rights on the system. prevents CWE-269