CVE-2026-55001
HIGH 7.8 ALL-YEARSImproper certificate validation in Windows Active Directory allows an authorized attacker to elevate privileges locally.
Severe if exploited (CVSS 7.8), but no confirmed exploitation. Patch on a normal cadence.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 22nd percentile
Impact if exploited
7.8CVSS 3.1 · HIGH · CNA
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ⚠Access: Requires local access to the host
- ⚠Privileges: Requires a low-privilege account
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.
Affected
Vendors Microsoft
Products Windows 10 Version 1607 Windows 10 Version 1809 Windows Server 2016 Windows Server 2016 (Server Core Installation) Windows Server 2019 Windows Server 2019 (Server Core Installation) Windows Server 2022 Windows Server 2025 Windows Server 2025 (Server Core Installation) Windows 10 1607 Windows 10 1809
Weakness (CWE)
- CWE-295: : Improper Certificate Validation
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
References and research data (JSON)
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Microsoft | Windows 10 1607 | < 10.0.14393.9339 |
| Microsoft | Windows 10 1607 | < 10.0.14393.9339 |
| Microsoft | Windows 10 1809 | < 10.0.17763.9020 |
| Microsoft | Windows 10 1809 | < 10.0.17763.9020 |
| Microsoft | Windows Server 2016 | < 10.0.14393.9339 |
| Microsoft | Windows Server 2019 | < 10.0.17763.9020 |
| Microsoft | Windows Server 2022 | < 10.0.20348.5386 |
| Microsoft | Windows Server 2025 | < 10.0.26100.33158 |
All CVSS metrics
- HIGH 7.8 v3.1 · CNA Primary
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - HIGH 7.8 v3.1 · NVD Secondary
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
Patches & mitigations
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55001 CVE record · microsoft · Updated 2026-10-08T18:13:06.984Z
NVD · CVE-2026-55001 · Updated 2026-07-24T14:18:05.577
Advisories
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-44010 EUVD · EUVD-2026-44010
Sources: NVD · CVE.org · All sources and attribution · EPSS