EUVD-2026-56635
GHSA-x8qw-26fx-j6r6
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
AV:A is correct as DHCP operates over Layer 2 broadcast; PR:N confirmed by unauthenticated DHCP protocol; C:H reflects memory disclosure potential; no integrity 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
Information disclosure in Windows DHCP Server across six major Windows Server generations exposes heap or stack memory contents to unauthenticated adjacent-network attackers via an integer underflow defect. The vulnerability affects all Windows Server editions from 2012 through 2025 that have the DHCP Server role installed and running, with exploitation constrained to Layer 2 adjacency rather than the open internet. A vendor-released patch is available from Microsoft MSRC; no public exploit code has been identified at time of analysis.
Technical ContextAI
The Windows DHCP Server role, which implements RFC 2131 over UDP ports 67/68, contains an integer underflow (wrap-around) defect classified under CWE-125 (Out-of-Bounds Read). When an arithmetic underflow occurs in a length or offset variable during DHCP packet processing, the resulting large wrapped value causes the server to read memory beyond the intended buffer boundary, potentially disclosing process memory contents to the requesting client. Affected versions span the full Windows Server lineage: Server 2012 (build 6.2.9200.x), Server 2012 R2 (6.3.9600.x), Server 2016 and Windows 10 v1607 (10.0.14393.x), Windows 10 v1809 and Server 2019 (10.0.17763.x), Server 2022 (10.0.20348.x), and Server 2025 (10.0.26100.x), including all Server Core installation variants. It is worth noting a metadata discrepancy: the advisory tags include 'Buffer Overflow,' but CWE-125 and the CVE description both describe a read-side out-of-bounds operation, not a write-side overflow - the root cause should be treated as an OOB read triggered by integer underflow, not a classic stack or heap write overflow.
RemediationAI
The primary fix is to apply the Microsoft-released security update for each affected platform, bringing builds to or above the following fixed versions: 10.0.26100.33296 (Windows Server 2025), 10.0.20348.5499 (Server 2022), 10.0.17763.9115 (Server 2019 and Windows 10 v1809), 10.0.14393.9418 (Server 2016 and Windows 10 v1607), 6.3.9600.23337 (Server 2012 R2), and 6.2.9200.26279 (Server 2012). Updates should be applied via Windows Update, WSUS, or Microsoft Update Catalog and the full advisory reviewed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62720. If patching cannot be performed immediately, a targeted compensating control is to apply network ACLs or firewall rules restricting UDP 67/68 traffic to the DHCP server so that only known, trusted client subnets can initiate DHCP exchanges - note this may break DHCP service for legitimate clients on restricted segments and must be coordinated with network operations. If the DHCP Server role is not operationally required on a given host, disabling and removing it eliminates the attack surface entirely with no service impact to other roles. There is no indication of a publicly available workaround specific to this integer underflow path.
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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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