CVE-2026-20817
Microsoft Windows 10 21H2 ≤ 10.0.19044.6809
Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-20817 is a high-severity Improper Handling of Insufficient Permissions or Privileges (CWE-280) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 7.8 (High).
Operationally, ranked in the top 8% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-24 (Access Control Decisions) and AC-25 (Reference Monitor) — 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-2026-20817 involves improper handling of insufficient permissions or privileges in Windows Error Reporting, enabling an authorized attacker to elevate privileges locally. This vulnerability affects the Windows Error Reporting component in Microsoft Windows operating systems and is classified under CWE-280. It received a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and was published on 2026-01-13T18:16:08.647.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity and no user interaction required. Successful exploitation allows the attacker to achieve high impacts on confidentiality, integrity, and availability, resulting in full privilege escalation on the affected system.
Microsoft's advisory provides details on mitigation and patches at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20817.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2188
Vulnerability Data
Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 6 hardening rules · 3 OS baselines
V6.2.2V8.3.3
Mitigating Controls (NIST 800-53 r5) AI
Ensuring access decisions are applied to every request structurally prevents the product from taking unexpected paths when privileges are lacking.
A reference monitor that is always invoked guarantees privilege checks occur, eliminating the root condition for improper insufficient-privilege handling.
Access enforcement directly stops code from proceeding on insufficient privileges by applying authorization checks before resource access.
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.
Defining, enforcing and reviewing access permissions with least privilege directly prevents code paths that mishandle insufficient privileges.
Runtime monitoring of software and data surfaces adverse events triggered by unhandled permission failures.
Generating logs of permission-related events enables detection and analysis of improper handling.
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.
Security testing can detect missing or incorrect privilege handling.
Defines access-control policy that should prevent insufficient-privilege situations.
Specifies how access rights are granted, reviewed and revoked, directly addressing privilege handling.
Requires explicit management of privileged access rights, reducing the chance of missing privilege checks.
Secure-SDLC practices include privilege checks during design and coding.
Secure-coding standards require proper permission checks before resource access.
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` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248548 OL 8 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-280
- V-248596 OL 8 must enable the SELinux targeted policy. prevents CWE-280
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-280
RHEL 9 (2 rules)
- V-258078 RHEL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-280
- V-272496 RHEL 9 must elevate the SELinux context when an administrator calls the sudo command. prevents CWE-280