What is CVE-2026-56159?
Heap-based buffer overflow in Windows DHCP Server allows an unauthorized attacker to execute code over a network.
The record classifies CVE-2026-56159 under weakness class CWE-122. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 12 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 106 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 0.9% probability of exploitation in the next 30 days, higher than 60.9% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 7.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-07-14, last modified 2026-10-08
Is CVE-2026-56159 being exploited?
It currently carries a trending score of 38 in the Threadlinqs vulnerability feed.
Affected products and versions
- Microsoft: Windows 10 Version 1607, Windows 10 Version 1809, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2025
How to fix CVE-2026-56159
No vendor patch reference has been recorded for CVE-2026-56159 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-56159
3 tracked threats in the Threadlinqs corpus reference CVE-2026-56159, either in the campaign’s CVE list or as an indicator on the campaign record.
- Microsoft July 2026 Patch Tuesday: 570 Flaws Fixed, 3 Zero-Days Including AD FS and SharePoint Privilege Escalation — CRITICAL · 2026-07-14
- Microsoft July 2026 Patch Tuesday: 569 CVEs, Two Actively Exploited Zero-Days (CVE-2026-56155 AD FS EoP, CVE-2026-56164 SharePoint EoP) — CRITICAL · 2026-07-14
- Microsoft July 2026 Patch Tuesday: Record 622 CVEs Include Two Actively Exploited Zero-Days in AD FS (CVE-2026-56155) and SharePoint Server (CVE-2026-56164) — CRITICAL · 2026-07-14
Sources
Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on .