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Windows CVE-2026-20849

HIGH
Reliance on Untrusted Inputs in a Security Decision (CWE-807)
2026-01-13 secure@microsoft.com
7.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
7.5 HIGH
AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Mar 12, 2026 - 21:54 vuln.today
CVE Published
Jan 13, 2026 - 18:16 nvd
HIGH 7.5

DescriptionCVE.org

Reliance on untrusted inputs in a security decision in Windows Kerberos allows an authorized attacker to elevate privileges over a network.

AnalysisAI

Windows Kerberos authentication in multiple Windows versions accepts untrusted input during security decisions, enabling authenticated network attackers to escalate privileges without user interaction. The vulnerability affects Windows 10 (versions 1607 and 1809), Windows Server 2012, and Windows Server 2025, with no patch currently available. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Authenticated attacker crafts malicious Kerberos token
Exploit
Exploit untrusted input in security decision logic
Execution
Bypass privilege validation checks
Impact
Elevate privileges to higher level

Vulnerability AssessmentAI

Exploitation Attacker must have valid domain credentials and network access to a Windows domain controller. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment CVSS 7.5 (HIGH). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario A remote attacker could exploit this vulnerability to compromise the affected system.
Remediation Monitor vendor advisories for a patch. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 7 days: Identify all affected systems and apply vendor patches promptly. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-20849 vulnerability details – vuln.today

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