Patch tracker / CVE reference / CVE-2026-56159

CVE-2026-56159

CVE-2026-56159 is a Microsoft vulnerability that Microsoft rates Critical, with a CVSS score of 9.8 (Critical). Microsoft has shipped the fix: deploy one of the 6 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

Critical

9.8

CVSS v3

4.9%

EPSS, 30 days

Critical

Severity

Not in the CISA KEV catalog. EPSS exploit probability 4.9%. CVSS 9.8 (Critical).

This CVE is among the top half of tracked Microsoft CVEs by EPSS exploit probability.

Senserva AI Opinion for CVE-2026-56159

This is a Critical (CVSS 9.9) remote code execution flaw in the Windows DHCP Server Service, meaning a networked attacker could run code on the server that hands out IP addresses to your environment. Exposure is limited to Windows Server 2019 hosts running the DHCP role plus Windows 10 Version 1809 systems, so infrastructure servers are the real concern here. EPSS estimates a 7 percent exploit probability and there is no confirmed exploitation yet, but a compromised DHCP server can pivot across an entire subnet.

Do this: Identify every Windows Server 2019 machine running the DHCP Server role and apply the Microsoft patch for CVE-2026-56159 to those first.

AI-generated from public data, 2026-07-24. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-56159

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin assessing a vulnerability. Facts for CVE-2026-56159 (source: https://senserva.com/cve/CVE-2026-56159.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed daily (early morning US Central)):
- CVE-2026-56159: Microsoft vulnerability, Microsoft rating Critical, CVSS 9.8 (Critical)
- EPSS 30-day exploitation probability: 4.9%
- Actively exploited (CISA KEV): no
- Fixed by: KB5099444, KB5099445, KB5099535, KB5099536, KB5099538, KB5099540
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Schedule normally

No exploitation observed as of 2026-10-14: not in the CISA KEV catalog, EPSS 5%.

Fixed by KB5099444 and 5 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Deploy with your normal update cycle. This page refreshes daily; the verdict changes the day the data does.

Official patch(es) for CVE-2026-56159

Elevated priority: high severity or a meaningful exploitation probability, sooner if an affected product is internet-facing. In Intune or Defender, confirm whether the fixing updates KB5099444, KB5099445, KB5099535, KB5099536, KB5099538, KB5099540 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Apply the Microsoft security updates below to fix CVE-2026-56159. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.

KB5099444 KB5099445 KB5099535 KB5099536 KB5099538 KB5099540

Scope and sources

Affected products

Fixed by the same updates

CVE-2026-56155 CVE-2026-32202 CVE-2026-57092 CVE-2026-42990 CVE-2026-49172 CVE-2026-50447 CVE-2026-50518 CVE-2026-54990

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC FIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.