CVE-2026-20858
Published: 13 January 2026
Summary
CVE-2026-20858 is a high-severity Race Condition (CWE-362) vulnerability in Microsoft Windows 10 1809. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 3.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-20858 is a use-after-free vulnerability in Windows Management Services, published on 2026-01-13. It affects Windows operating systems and is linked to CWE-416 (use after free) and CWE-362 (race condition). The vulnerability carries a CVSS v3.1 base score of 7.8 (High), with vector AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H, indicating local attack vector, high attack complexity, low privileges required, no user interaction, changed scope, and high impacts across confidentiality, integrity, and availability.
A local attacker with low privileges (PR:L) can exploit this vulnerability due to the use-after-free flaw in Windows Management Services. Exploitation requires high complexity (AC:H) but no user interaction (UI:N). Successful exploitation enables privilege escalation, allowing the attacker to gain elevated access on the system with high confidentiality, integrity, and availability impacts under a changed scope (S:C).
Microsoft's Security Response Center provides details on the vulnerability, including patches and mitigation guidance, in their update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20858.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2149
Vulnerability details
Use after free in Windows Management Services allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local use-after-free in Windows Management Services directly enables privilege escalation (T1068) with high impact under changed scope.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly remediates the use-after-free vulnerability in Windows Management Services by requiring timely application of vendor patches.
Implements memory safeguards such as DEP, ASLR, and control-flow integrity to protect against exploitation of use-after-free flaws leading to privilege escalation.
Enforces least privilege on processes like Windows Management Services to limit the impact and success of local privilege escalation attempts.