EUVD-2026-56636
GHSA-54r7-32cv-3934
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Adjacent-network vector matches DHCP protocol scope; no privileges or interaction required per the nature of DHCP; confidentiality-only impact reflects an out-of-bounds read with no write or availability consequence.
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
Information disclosure in the Windows DHCP Server service allows unauthenticated attackers on adjacent network segments to read out-of-bounds server memory via a malformed DHCP request that triggers an integer underflow. Affected builds span Windows Server 2012 through Windows Server 2025, as well as Windows 10 versions 1607 and 1809, making the version footprint unusually wide for a single service-role flaw. No public exploit has been identified at time of analysis and CISA's SSVC framework rates exploitation as none with non-automatable characteristics, though the high confidentiality impact and the breadth of affected builds warrant prompt patching.
Technical ContextAI
The Windows DHCP Server service implements RFC-compliant Dynamic Host Configuration Protocol handling for address assignment across Layer 2 and Layer 3 network boundaries. The root cause is an integer underflow mapped to CWE-125 (Out-of-bounds Read): a length or offset value is decremented without a non-negative guard, wrapping to a very large unsigned integer that causes the service to read memory well beyond the intended packet buffer. This is a classic arithmetic wrap class of bug, distinct from a heap or stack overflow write - it enables memory disclosure rather than code execution, which is consistent with the CVSS impact of C:H/I:N/A:N. The CVSS attack vector of AV:A confirms exploitation is bounded to the same broadcast domain or directly adjacent subnet, matching DHCP's inherent Layer 2/3 scope. Affected builds per EUVD-2026-56636 range from Windows Server 2012 (build 6.2.9200.x) through Windows Server 2025 (build 10.0.26100.x), as well as Windows 10 releases still running the DHCP server role. The reporter is secure@microsoft.com, confirming Microsoft's own security team sourced the report.
RemediationAI
Apply Microsoft's security updates for each affected platform to reach the fixed build thresholds: 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. The specific KB article numbers for each build should be retrieved from the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62714. Note that Windows Server 2012 and Windows Server 2012 R2 are past standard support lifecycle and require active Extended Security Updates (ESU) entitlement to receive this patch - organizations without ESU coverage should prioritize migration. As a compensating control where immediate patching is not feasible, enforce Layer 2 segmentation using 802.1X port authentication or VLAN ACLs to restrict which hosts can reach the DHCP server's UDP ports (67/68), reducing the adjacent-network attack surface; this does not eliminate risk but raises the bar for exploitation.
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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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