Windows DNS Server: Out-of-bounds write allows remote code execution
Summary
An out-of-bounds write in the Windows DNS Server role allows an attacker to execute code over the network. The CVSS 3.1 base score is 8.8. Exploitation requires a valid low-privileged account, and no user interaction is needed. The vendor's CVE record lists affected Windows Server 2016, 2019, 2022 and 2025 builds; no exploitation information was found at the time of writing.
Affected
- Windows Server 2016 (including Server Core): 10.0.14393.0 to below 10.0.14393.9688
- Windows Server 2019 (including Server Core): 10.0.17763.0 to below 10.0.17763.9487
- Windows Server 2022: 10.0.20348.0 to below 10.0.20348.5870
- Windows Server 2025 (including Server Core): 10.0.26100.0 to below 10.0.26100.33822
Fixed in
- Install the Microsoft security update for the affected versions.
- Builds that fix the issue according to the CVE record: 10.0.14393.9688 (2016), 10.0.17763.9487 (2019), 10.0.20348.5870 (2022), 10.0.26100.33822 (2025).
- KB numbers: Unknown.
Workaround
- None known. Unknown.
Exploitation
- Unknown. No KEV listing, public proof of concept or exploitation report was found at the time of writing.
Our recommendation
- Check whether the Windows DNS Server role is installed, especially on domain controllers.
- Apply the Microsoft security update to DNS servers first once the MSRC page confirms the fix.
- Restrict dynamic DNS updates and limit access to the DNS service.
- Monitor DNS server logs and restrict administrative access.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – Role: DNS Server
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- 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
- Microsoft Security Update Guide: CVE-2026-96020 msrc.microsoft.com
- Qualys: Windows DNS Server out-of-bounds write (CVE-2021-26897), generic DNS hardening threatprotect.qualys.com
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 10 Nov 2026, 20:52.
Original description (NVD)
Out-of-bounds write in DNS Server allows an authorized attacker to execute code 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.