EUVD-2026-56370
GHSA-cr3j-p872-8mv4
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Adjacent network access required; no auth or user interaction needed; impact is read-only memory disclosure with no integrity 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
Integer underflow (CWE-125) in the Windows DHCP Server service exposes server memory contents to unauthenticated attackers positioned on the same adjacent network segment. Affecting Windows Server versions from 2012 through 2025 (confirmed by ENISA EUVD-2026-56370), the flaw allows crafted DHCP packets to trigger an out-of-bounds read, resulting in high-confidence confidentiality impact with no integrity or availability consequences. No public exploit code has been identified at time of analysis, and CISA SSVC rates exploitation status as none with partial technical impact - a vendor patch is available via Microsoft MSRC.
Technical ContextAI
The vulnerability resides in the Windows DHCP Server role service, which processes RFC 2131 DHCP messages over UDP ports 67/68. CWE-125 (Out-of-Bounds Read) is the root cause class - an integer underflow (wrap-around) in a length or offset calculation causes the service to read memory beyond the intended buffer boundary when processing a malformed client packet. This class of flaw commonly arises when a subtraction on an unsigned integer produces a very large positive value rather than a negative result, causing subsequent memory access to fall outside allocated regions. The adjacent network attack vector (AV:A) is consistent with DHCP's Layer 2 broadcast domain operation: an attacker must be on the same network segment as the DHCP server, or reach it through a DHCP relay (UDP helper). Affected builds span a broad CPE range: Windows Server 2012 (6.2.x), 2012 R2 (6.3.x), 2016 (10.0.14393.x), 2019 (10.0.17763.x), 2022 (10.0.20348.x), and 2025 (10.0.26100.x), as well as Windows 10 versions 1607 and 1809 where the DHCP Server role is enabled.
RemediationAI
Apply Microsoft-released updates to reach the following minimum fixed build versions: Windows Server 2012 to 6.2.9200.26279, Windows Server 2012 R2 to 6.3.9600.23337, Windows Server 2016 to 10.0.14393.9418, Windows Server 2019 to 10.0.17763.9115, Windows Server 2022 to 10.0.20348.5499, and Windows Server 2025 to 10.0.26100.33296. Updates are available via Windows Update, WSUS, and the Microsoft Update Catalog as documented at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62745. As a compensating control prior to patching, apply network ACLs or host-based firewall rules to restrict inbound UDP port 67 traffic to the DHCP server to only known authorized client subnets and trusted DHCP relay agent addresses - this confines the adjacent-network attack surface to trusted segments and prevents exploitation from arbitrary internal subnets. Trade-off: overly restrictive ACLs may prevent legitimate DHCP relay forwarding from remote subnets, disrupting address assignment for those clients. Disabling the DHCP Server service entirely is effective but will halt all address assignment for served clients until an alternative is in place.
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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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