Microsoft Windows Server DNS Server: Denial of service via use-after-free
Summary
A use-after-free vulnerability in the DNS Server role of Windows Server allows an authorized attacker to cause a denial of service over the network. The attacker needs high privileges, such as administrative access, before the flaw can be triggered. The impact is limited to availability: an affected DNS server may stop answering name resolution requests, which can also disrupt authentication on domain controllers.
Affected
- Windows Server 2016 (incl. Server Core): builds 10.0.14393.0 before 10.0.14393.9688
- Windows Server 2019 (incl. Server Core): builds 10.0.17763.0 before 10.0.17763.9487
- Windows Server 2022: builds 10.0.20348.0 before 10.0.20348.5870
- Windows Server 2025 (incl. Server Core): builds 10.0.26100.0 before 10.0.26100.33822
Fixed in
- Windows Server 2016 (incl. Server Core): build 10.0.14393.9688 or later (KB number: unknown)
- Windows Server 2019 (incl. Server Core): build 10.0.17763.9487 or later (KB number: unknown)
- Windows Server 2022: build 10.0.20348.5870 or later (KB5131090)
- Windows Server 2025 (incl. Server Core): build 10.0.26100.33822 or later (KB5131080)
Workaround
Unknown.
Exploitation
- Not known to be exploited in the wild.
- No public proof-of-concept or exploit code known.
- CISA SSVC: exploitation none, not automatable.
Our recommendation
- Install the November 2026 security updates on all Windows Server systems with the DNS Server role, starting with domain controllers and internal DNS servers.
- Verify the installed build against the fixed builds listed above.
- Restrict administrative access to DNS servers to reduce the risk of misuse of the high privileges required.
- Monitor DNS service availability and check for a public exploit or a CISA KEV entry, as the status may change.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Role: DNS Server
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131291, KB5131085, KB5131090, KB5131080, KB5131077
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-96017 www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- Rapid7 Patch Tuesday November 2026 www.rapid7.com
- KB5131080 summary (Windows Server 2025) senserva.com
- KB5131090 summary (Windows Server 2022) senserva.com
- VulDB entry 435404 vuldb.com
- Strix CVE entry CVE-2026-96017 www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 19:37.
Original description (NVD)
Use after free in DNS Server allows an authorized attacker to deny service over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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