EUVD-2026-56400
GHSA-6f49-r342-pg5p
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Unauthenticated network exploitation of a DNS service with no user interaction and memory-corruption RCE yields AV:N/AC:L/PR:N/UI:N and full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Stack-based buffer overflow in Windows DNS allows an unauthorized attacker to execute code over a network.
AnalysisAI
Remote code execution in the Windows DNS component allows an unauthenticated network attacker to run arbitrary code by triggering a stack-based buffer overflow (CWE-121). The flaw affects a broad range of Microsoft platforms from Windows 10 1607/1809 through Windows Server 2012 to Server 2025, including Server Core installations, and carries a CVSS 9.8 rating with no required privileges or user interaction. Microsoft has shipped fixes; there is no public exploit identified at time of analysis and the issue is not listed in CISA KEV.
Technical ContextAI
The vulnerability lives in Windows DNS, the name-resolution stack that ships with all supported Windows client and server editions; on server SKUs this is typically the DNS Server role that answers queries on UDP/TCP 53, while client editions run the DNS client resolver. CWE-121 (stack-based buffer overflow) means attacker-controlled data - most plausibly an oversized or malformed DNS message field - is copied into a fixed-size stack buffer without adequate bounds checking, corrupting the stack (return address / saved registers) and enabling control-flow hijack. Because DNS parsing runs in a privileged system service, successful memory corruption typically yields code execution in a high-privilege context. The EUVD-listed builds indicate the fix spans the Windows 10 1607/1809 servicing branches (14393/17763) and every Server branch through 26100 (Server 2025).
RemediationAI
Apply the Microsoft security update for CVE-2026-62878 (patch available per vendor advisory) - install the cumulative update that raises the DNS/OS build to at least the fixed version for your SKU: 10.0.17763.9115 (Windows 10 1809 / Server 2019), 10.0.14393.9418 (Windows 10 1607 / Server 2016), 6.2.9200.26279 (Server 2012), 6.3.9600.23337 (Server 2012 R2), 10.0.20348.5499 (Server 2022), or 10.0.26100.33296 (Server 2025), per https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62878. Prioritize internet-exposed and internal DNS servers first. As compensating controls until patching completes, restrict inbound DNS (UDP/TCP 53) to only trusted resolvers and clients via host and perimeter firewall rules, and remove any unnecessary internet exposure of the DNS Server role - the trade-off is that overly tight source restrictions can break legitimate resolution for remote clients and forwarders, so validate query paths before enforcing. Where the DNS Server role is not required, disabling it eliminates the server-side attack surface entirely, at the cost of losing local name-resolution services.
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Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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