CVE-2026-56155: Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 14 Jul 2026, the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 0.3%
EPSS score, percentile 28.1 of all scored records
- How severe?
- 7.8 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline 28 Jul 2026. Apply mitigations in accordance with vendor instructions … Full text
- Which versions are affected?
Affected
- from 10.0.14393.0 to before 10.0.14393.9339
- from 10.0.17763.0 to before 10.0.17763.9020
- from 6.2.9200.0 to before 6.2.9200.26226
- from 6.2.9200.0 to before 6.2.9200.26226
- from 6.3.9600.0 to before 6.3.9600.23291
- from 6.3.9600.0 to before 6.3.9600.23291
and 7 more in the table below
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: 28 July 2026.
Advisories and patches
Linked from CISA's catalog entry
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-56155
- 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-2026-56155
- https://learn.microsoft.com/en-us/windows-server/identity/ad-fs/decommission/adfs-decommission-guide
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 10.0.14393.0 to before 10.0.14393.9339 |
| Status | Versions |
|---|---|
| Affected | from 10.0.17763.0 to before 10.0.17763.9020 |
| Status | Versions |
|---|---|
| Affected | from 6.2.9200.0 to before 6.2.9200.26226 |
| Status | Versions |
|---|---|
| Affected | from 6.2.9200.0 to before 6.2.9200.26226 |
| Status | Versions |
|---|---|
| Affected | from 6.3.9600.0 to before 6.3.9600.23291 |
| Status | Versions |
|---|---|
| Affected | from 6.3.9600.0 to before 6.3.9600.23291 |
| Status | Versions |
|---|---|
| Affected | from 10.0.14393.0 to before 10.0.14393.9339 |
| Status | Versions |
|---|---|
| Affected | from 10.0.14393.0 to before 10.0.14393.9339 |
| Status | Versions |
|---|---|
| Affected | from 10.0.17763.0 to before 10.0.17763.9020 |
| Status | Versions |
|---|---|
| Affected | from 10.0.17763.0 to before 10.0.17763.9020 |
| Status | Versions |
|---|---|
| Affected | from 10.0.20348.0 to before 10.0.20348.5386 |
| Status | Versions |
|---|---|
| Affected | from 10.0.26100.0 to before 10.0.26100.33158 |
| Status | Versions |
|---|---|
| Affected | from 10.0.26100.0 to before 10.0.26100.33158 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Microsoft Active Directory Federation Services contains an insufficient granularity of access control vulnerability that allows an authorized attacker to elevate privileges locally.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2026-56155 to its Known Exploited Vulnerabilities (KEV) catalog on 14 Jul 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 28 Jul 2026.
- The CVE record was published on 14 Jul 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 0.3% (percentile 28.1), 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
Active Directory Federation Services Elevation of Privilege Vulnerability
Insufficient granularity of access control in Active Directory Federation Services (AD FS) 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-1220: Insufficient Granularity of 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 |
|---|---|
| 14 Jul 2026 | CVE record published |
| 14 Jul 2026 | Added to CISA KEV |
| 28 Jul 2026 | CISA due date for the required action |
| 8 Oct 2026 | CVE record last updated |
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