EUVD-2026-56587
GHSA-q5gh-vjhc-39x9
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector and low-privilege requirement match the 'authorized local attacker' description; no user interaction or scope change; full CIA impact consistent with SYSTEM-level privilege escalation.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
7DescriptionNVD
Heap-based buffer overflow in Windows DNS allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation via heap-based buffer overflow in the Windows DNS component affects Windows 10, Windows 11, and Windows Server editions spanning Server 2012 through Server 2025. An authorized local attacker holding low-privilege credentials can trigger the overflow to achieve full system compromise (C:H/I:H/A:H). No public exploit code or active exploitation has been identified at time of analysis; a vendor-released patch is available through the Microsoft Security Response Center advisory.
Technical ContextAI
CWE-122 (Heap-based Buffer Overflow) describes a condition where a heap-allocated buffer is written beyond its allocated bounds, enabling corruption of adjacent heap metadata or data structures. The vulnerable component is the Windows DNS subsystem - present as a DNS client on all Windows workstations and optionally as a DNS Server role on Windows Server editions. CPE strings confirm affected platforms include Windows 10 versions 1607, 1809, 21H2, and 22H2 across x86, x64, and ARM64 architectures; tags extend confirmed impact to Windows 11 (23H2 through 26H1) and Windows Server 2012 through 2025. Heap overflows in OS-level DNS parsing code can enable reliable privilege escalation because an attacker who already controls a local execution context can often manipulate heap layout to redirect control flow toward attacker-controlled code.
RemediationAI
Apply the Microsoft-released patches via Windows Update or the Microsoft Update Catalog targeting the minimum fixed build for each OS version as documented in EUVD-2026-56587 and the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70330. For Windows Server systems running the DNS Server role, prioritize patching immediately given the elevated sensitivity of DNS infrastructure to local privileged compromise. Where immediate patching is not feasible, restrict local interactive logon and remote desktop rights on DNS-hosting servers to only essential administrative accounts, directly reducing the pool of principals who satisfy the PR:L prerequisite. Where the Windows DNS Server role is not required on a given host, consider disabling the role until the patch is applied - note this disables name resolution hosting, which will impact AD-integrated DNS environments and must be tested carefully. Restricting logon rights may interfere with legitimate remote management workflows and requires change-control review before deployment.
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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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