CVE-2026-81963 (GCVE-0-2026-81963)

Vulnerability from cvelistv5 – Published: 2026-09-08 17:19 – Updated: 2026-09-18 20:46
VLAI CISA Previdian
Title
Windows Update Stack Elevation of Privilege Vulnerability
Summary
Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
SSVC
Exploitation: active Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-07 00:00 UTC
CWE
  • CWE-59 - Improper Link Resolution Before File Access ('Link Following')
  • CWE-284 - Improper Access Control
Assigner
References
Impacted products
Vendor Product Version CPE status
Microsoft Windows 11 version 23H2 Affected: 10.0.22631.0 , < 10.0.22631.7582 (custom)
guessed Create a notification for this product.
Microsoft Windows 11 Version 23H2 Affected: 10.0.22631.0 , < 10.0.22631.7582 (custom)
guessed Create a notification for this product.
Microsoft Windows 11 Version 24H2 Affected: 10.0.26100.0 , < 10.0.26100.9445 (custom)
guessed Create a notification for this product.
Microsoft Windows 11 Version 25H2 Affected: 10.0.26200.0 , < 10.0.26200.9445 (custom)
guessed Create a notification for this product.
Microsoft Windows 11 version 26H1 Affected: 10.0.28000.0 , < 10.0.28000.2954 (custom)
guessed Create a notification for this product.
Microsoft Windows Server 2025 Affected: 10.0.26100.0 , < 10.0.26100.33438 (custom)
guessed Create a notification for this product.
Microsoft Windows Server 2025 (Server Core installation) Affected: 10.0.26100.0 , < 10.0.26100.33438 (custom)
guessed Create a notification for this product.
Date Public
2026-09-08 14:00
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 09991baa-5ae1-426a-8367-a5205a9ff1b1

Vulnerability ID: CVE-2026-81963

Status: Confirmed

Status Updated: 2026-09-08 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2026-09-08
Asserted: 2026-09-08
Scope
Notes: Microsoft Windows Link Following Vulnerability | Affected: Microsoft / Windows | Description: Microsoft Windows Update Stack contains a link following vulnerability that allows a local attacker to escalate privileges locally up to SYSTEM. | Required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. | Due date: 2026-09-22 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-81963 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-81963
Evidence

Type: Vendor Report

Signal: Successful Exploitation

Confidence: 80%

Source: cisa-kev

Details
Cwes CWE-59 CWE-284
Feed CISA Known Exploited Vulnerabilities Catalog
Product Windows
Due Date 2026-09-22
Date Added 2026-09-08
Vendorproject Microsoft
Vulnerabilityname Microsoft Windows Link Following Vulnerability
Knownransomwarecampaignuse Unknown
References
Created: 2026-09-08 19:00 UTC | Updated: 2026-09-08 19:00 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 67a434d0-13fb-4575-919e-d58492f0b1fa

Vulnerability ID: CVE-2026-81963

Status: Confirmed

Status Updated: 2026-09-08 07:00 UTC

Exploited: Yes

Timestamps
First Seen: 2026-09-08
Asserted: 2026-09-08
Scope
Notes: Windows Update Stack Elevation of Privilege Vulnerability | Affected: Microsoft / Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2025, Windows Server 2025 (Server Core installation) | CVSS: 7.8 (HIGH) | Used in malware: unknown | Not yet in CISA KEV: False
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: previdian

Details
Feed Previdian (previdian.com)
Title Windows Update Stack Elevation of Privilege Vulnerability
Vendor Microsoft
Product Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2025, Windows Server 2025 (Server Core installation)
Added Date 2026-09-08T07:00:00.000Z
Cvss Score 7.8
Epss Score None
Cvss Severity HIGH
Epss Percentile None
Used In Malware unknown
Ahead Of Cisa Kev 
{
  "count": 12,
  "unit": "hour"
}
Not Yet In Cisa Kev False
References
Created: 2026-09-09 07:01 UTC | Updated: 2026-09-09 07:01 UTC
Show details on NVD website
To clipboard 

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}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.