CVE-2026-56155
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
do firstApply 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.
Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.
Also consider: patch
Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2026-56155 being exploited?
Yes. CVE-2026-56155 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2026-56155?
CVE-2026-56155 is rated High with a CVSS score of 7.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-56155?
Yes. A fix has been recorded for CVE-2026-56155. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-56155 affect?
CVE-2026-56155 affects microsoft:windows_10_1607, microsoft:windows_10_1809, microsoft:windows_server_2012, microsoft:windows_server_2016, and 3 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.20348.0 and < 10.0.20348.5386
- affected>= 10.0.26100.0 and < 10.0.26100.33158
- affected>= 10.0.26100.0 and < 10.0.26100.33158
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 15 Jul 2026 (SSVC 2.0.3).
timeline
- 14 Jul 2026Added to CISA KEV (exploited in the wild)
- 14 Jul 2026Published · 1 day later
- 15 Jul 2026CISA SSVC assessment: exploitation active · same day later
- 28 Jul 2026CISA remediation due date (US federal agencies) · 13 days later
- 1 Nov 2026CVE record last updated · 97 days (about 3 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 1 day later
- Patchmsrc.microsoft.com /update-guide/vulnerability/CVE-2026-56155
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56155
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.