EUVD-2026-56682
GHSA-632v-rmmc-3pm8
Severity by source
AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Local attack requiring high privileges to reach the DNS heap overflow; unchanged scope with full CIA impact consistent with escalation to SYSTEM from an already-privileged context.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Numeric truncation error in Windows DNS allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation in Windows DNS across a broad range of Microsoft Windows releases stems from a numeric truncation error (CWE-122) that produces a heap-based buffer overflow, enabling an already high-privileged local attacker to escalate further - likely to SYSTEM level. The vulnerability spans Windows Server 2012 through Server 2025 and Windows 10/11 consumer editions, representing a wide patching surface. No public exploit has been identified at time of analysis, and CISA SSVC confirms exploitation status as none with no automatable attack path, though technical impact is rated total.
Technical ContextAI
The flaw resides in the Windows DNS component - present in both the DNS Server role on Windows Server editions and the DNS client stack on workstation editions. The root cause is CWE-122 (Heap-based Buffer Overflow) induced by a numeric truncation error: a value silently narrows when assigned to a smaller integer type, producing an incorrect size or offset calculation that under-allocates or mis-bounds a heap buffer. Subsequent writes overflow into adjacent heap memory, potentially corrupting metadata or function pointers in a way that redirects execution. The affected CPE surface spans Windows NT kernel builds from 6.2.x (Server 2012) through 10.0.28000.x (Windows 11 26H1), as confirmed by EUVD-2026-56682. The DNS service on Windows Server editions runs under elevated context, making this component a high-value target for post-exploitation privilege escalation chains.
RemediationAI
Apply Microsoft's vendor-released cumulative updates targeting the exact build thresholds confirmed in EUVD-2026-56682: update Windows Server 2025 to build 10.0.26100.33296 or later, Server 2022 to 10.0.20348.5499 or later, Server 2019 and Windows 10 1809 to 10.0.17763.9115 or later, Server 2016 and Windows 10 1607 to 10.0.14393.9418 or later, Server 2012 R2 to 6.3.9600.23337 or later, Server 2012 to 6.2.9200.26279 or later, and Windows 11 editions to their respective thresholds listed above. Updates are distributed through Windows Update, WSUS, and the Microsoft Update Catalog; the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62881 provides direct patch links. For systems where immediate patching is not feasible - particularly legacy Server 2012/2012 R2 which may require Extended Security Updates - enforce strict least-privilege access controls to minimize the pool of accounts that hold the high local privileges required to trigger this flaw; this does not eliminate the vulnerability but limits its exploitability. Additionally, auditing and restricting who can interact with DNS service management interfaces on affected hosts reduces exposure in post-compromise scenarios.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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