CVE-2026-81963: Microsoft Windows Link Following Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 8 Sep 2026, the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 0.4%
EPSS score, percentile 33.4 of all scored records
- How severe?
- 7.8 High
CVSS v3.1 base score, given by the CNA
- What should I do?
Required action (CISA), due 22 Sep 2026: 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.
- Which versions are affected?
Affected: 10.0.22631.0 up to, not including, 10.0.22631.7582; 10.0.22631.0 up to, not including, 10.0.22631.7582; 10.0.26100.0 up to, not including, 10.0.26100.9445; 10.0.26200.0 up to, not including, 10.0.26200.9445; 10.0.28000.0 up to, not including, 10.0.28000.2954; 10.0.26100.0 up to, not including, 10.0.26100.33438; 10.0.26100.0 up to, not including, 10.0.26100.33438
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
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.
CISA due date for this action: 22 September 2026.
Advisories and patches
Linked from CISA's catalog entry
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-81963
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- 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
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 10.0.22631.0 up to, not including, 10.0.22631.7582 |
| Status | Versions |
|---|---|
| Affected | 10.0.22631.0 up to, not including, 10.0.22631.7582 |
| Status | Versions |
|---|---|
| Affected | 10.0.26100.0 up to, not including, 10.0.26100.9445 |
| Status | Versions |
|---|---|
| Affected | 10.0.26200.0 up to, not including, 10.0.26200.9445 |
| Status | Versions |
|---|---|
| Affected | 10.0.28000.0 up to, not including, 10.0.28000.2954 |
| Status | Versions |
|---|---|
| Affected | 10.0.26100.0 up to, not including, 10.0.26100.33438 |
| Status | Versions |
|---|---|
| Affected | 10.0.26100.0 up to, not including, 10.0.26100.33438 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Microsoft Windows Update Stack contains a link following vulnerability that allows a local attacker to escalate privileges locally up to SYSTEM.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2026-81963 to its Known Exploited Vulnerabilities (KEV) catalog on 8 Sep 2026.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 22 Sep 2026.
- The CVE record was published on 8 Sep 2026, the same day it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 7.8 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 33.4), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
Windows Update Stack Elevation of Privilege Vulnerability
Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-59: Improper Link Resolution Before File Access ('Link Following')
- CWE-284: Improper Access Control
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 8 Sep 2026 | CVE record published |
| 8 Sep 2026 | Added to CISA KEV |
| 22 Sep 2026 | CISA due date for the required action |
| 14 Oct 2026 | CVE record last updated |
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