EUVD-2026-56674
GHSA-248v-fmcv-3gc5
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
DHCP is inherently pre-authentication (PR:N) and adjacent-only (AV:A); out-of-bounds read causes confidentiality loss only, with no write or availability impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Integer underflow (wrap or wraparound) in Windows DHCP Server allows an unauthorized attacker to disclose information over an adjacent network.
AnalysisAI
Integer underflow in the Windows DHCP Server service exposes adjacent-network unauthenticated attackers to high-confidentiality memory disclosure across a broad range of Windows Server releases from 2012 through 2025, plus Windows 10 1607 and 1809. The root cause (CWE-125 out-of-bounds read triggered by arithmetic underflow) allows a crafted DHCP packet to cause the server to read and return memory beyond the intended buffer boundary. No active exploitation is confirmed (not in CISA KEV) and SSVC rates exploitation status as none; a vendor patch is available via the Microsoft Security Response Center.
Technical ContextAI
The affected component is the DHCP Server role in Windows, which processes UDP-based lease request packets from adjacent clients on port 67. An integer underflow - where an arithmetic operation on a length or offset field produces a value smaller than the valid minimum - causes subsequent memory access to extend beyond the intended buffer boundary, constituting CWE-125 (Out-of-Bounds Read). Because DHCP is a pre-authentication, stateless protocol, no session or credential is required to submit a packet. The vulnerability manifests during packet parsing before any access control is applied. Affected CPE covers Windows Server 2012 (6.2.9200.x), Server 2012 R2 (6.3.9600.x), Server 2016 (10.0.14393.x), Server 2019 (10.0.17763.x), Server 2022 (10.0.20348.x), Server 2025 (10.0.26100.x), and Windows 10 versions 1607 and 1809. Microsoft tags this as 'Buffer Overflow' in addition to 'Information Disclosure', which is consistent with an underflow enabling an over-read of stack or heap memory.
RemediationAI
Apply the Microsoft security update referenced at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62814 to bring affected systems to the fixed builds: Windows Server 2012 to 6.2.9200.26279 or later, Windows Server 2012 R2 to 6.3.9600.23337 or later, Windows Server 2016 to 10.0.14393.9418 or later, Windows Server 2019 to 10.0.17763.9115 or later, Windows Server 2022 to 10.0.20348.5499 or later, and Windows Server 2025 to 10.0.26100.33296 or later. Where immediate patching is not feasible, restrict UDP ports 67 and 68 to authorized DHCP relay agents and client subnets using host-based Windows Firewall rules or upstream network ACLs; note this reduces but does not eliminate risk from hosts already permitted on those segments. If the DHCP Server role is not required on a given host, removing it via Server Manager or PowerShell ('Remove-WindowsFeature DHCP') is the most definitive interim control, though this will disrupt IP address assignment for any clients depending on that server.
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Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
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External POC / Exploit Code
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