Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-20816 is a high-severity Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367) vulnerability in Microsoft Windows Server 2008. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked in the top 17% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — 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-2026-20816 is a time-of-check time-of-use (TOCTOU) race condition vulnerability in Windows Installer, affecting Windows operating systems. Classified under CWE-367, it enables local privilege escalation for authorized attackers. The vulnerability 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), indicating high severity due to its potential for significant impact on confidentiality, integrity, and availability with low complexity and privileges required.
An attacker with local access and low-level privileges (PR:L) can exploit this race condition in Windows Installer to elevate their privileges. By racing the time-of-check against time-of-use mechanism, the attacker can manipulate the installation process, potentially gaining higher privileges on the system and achieving high-impact outcomes across confidentiality, integrity, and availability.
The Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20816 provides details on mitigation, including available patches and recommended actions for affected Windows systems. Security practitioners should consult this reference for specific update guidance to address the vulnerability.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2200
Vulnerability Data
Time-of-check time-of-use (toctou) race condition in Windows Installer allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V15.4.2V17.2.6
Mitigating Controls (NIST 800-53 r5) AI
A reference monitor that is always invoked and analyzable structurally eliminates the non-atomic check-then-use pattern underlying TOCTOU.
Access enforcement that performs an atomic check-and-use decision directly stops the window in which a TOCTOU race can be exploited.
Process isolation limits the blast radius of a successful TOCTOU exploitation but does not remove the race itself.
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.
Secure SDLC practices directly include coding standards and reviews that prevent TOCTOU race conditions.
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.
Reliable, synchronized time across systems narrows the exploitable window in which a resource state can change between a security check and its use.