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CISA KEV · ACTIVELY EXPLOITED
HIGH severity

CVE-2026-56155 — Windows 10 1607

HIGH

CVE-2026-56155 is a high-severity (CVSS 7.8) CWE-1220 vulnerability in microsoft windows 10 1607. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-07-14) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.

Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.

Published
Updated
Affected
7 products
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-07-14. Federal agencies were required to remediate by 2026-07-28.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-56155.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs26th percentile — riskier than 26% of all scored CVEsHighest risk
0.00%0.98%1.95%2.93%2.3%0.3%0.3%0.3%Aug 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-56155 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.

Affected Products

7 products · 10 configurations
OS
windows 10 1607microsoft
< 10.0.14393.9339
range
OS
windows 10 1809microsoft
< 10.0.17763.9020
range
OS
windows server 2012microsoft
1 version
r2
OS
windows server 2016microsoft
< 10.0.14393.9339
range
OS
windows server 2019microsoft
< 10.0.17763.9020
range
OS
windows server 2022microsoft
< 10.0.20348.5386
range

Detection & mitigation playbook

Vendor / appliance

  1. Detect

    Inventory every microsoft windows 10 1607 deployment and check each version against the affected-products list above.

  2. Fix

    Apply the microsoft windows 10 1607 security patch or hotfix for CVE-2026-56155 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
O3 Security · Runtime Protection

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CVE-2026-56155: Windows 10 1607 (High 7.8, KEV)