Security readout for executives and security teams
Plain-English summary
A low-privilege, authorized attacker could abuse how Windows Kerberos trusts input when making a security decision, potentially gaining higher privileges remotely. Successful exploitation could compromise sensitive data, system integrity, and availability. Exploitation is rated high complexity and requires no user interaction.
Executive priority
Treat as a high-priority patching issue, especially on affected servers and high-value systems. The potential impact is severe, although exploitation requires existing access and high complexity. Confirm exposure promptly and deploy Microsoft’s applicable update after focused compatibility testing.
Technical view
CVE-2026-20849 is a CWE-807 flaw in Windows Kerberos involving reliance on untrusted input in a security decision. Its CVSS 3.1 score is 7.5: network-accessible, high complexity, low privileges required, no user interaction, unchanged scope, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure includes the listed Windows 10, Windows 11, and Windows Server releases, including Server Core variants. Organizations should prioritize affected servers and high-value Windows systems using Kerberos authentication. The bundle does not provide precise vulnerable build ranges or exclusions beyond the listed versions.
Exploitation context
The attacker must already have low-level authorization and successfully satisfy high-complexity conditions over a network. No user interaction is required. The supplied bundle reports that this CVE is not in KEV and provides no evidence of active exploitation or a public proof of concept.
Researcher notes
The sources identify the weakness class, affected releases, CVSS vector, and vendor advisory, but omit detailed attack preconditions, vulnerable code paths, update identifiers, and detection indicators. Researchers should avoid inferring exploitability beyond the documented authorized-network-attacker and high-complexity requirements.
Mitigation direction
- Review the Microsoft advisory for the exact update applicable to each affected Windows release.
- Apply Microsoft's security update using expedited, risk-based change control.
- Prioritize affected servers and Windows systems handling sensitive or privileged operations.
- If patching is delayed, follow only interim protections documented by Microsoft.
Validation and detection
- Inventory Windows editions and versions against the affected-product list.
- Confirm applicable Microsoft security updates are installed successfully on every affected asset.
- Retest Kerberos authentication and privileged workflows after updating.
- Review security monitoring for unexplained privilege changes or anomalous Kerberos activity.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-807: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-20849 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.65.9microsoftVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Windows Kerberos Elevation of Privilege VulnerabilityCVE reference, microsoft · vendor-advisory, patch
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Reliance on Untrusted Inputs in a Security Decision
Reliance on Untrusted Inputs in a Security Decision represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.