CVE-2026-62715 Overview
CVE-2026-62715 is an integer underflow vulnerability in the Windows DHCP Server service. The flaw allows an unauthenticated attacker on an adjacent network to disclose sensitive memory contents from the DHCP Server process. Microsoft classifies the issue under [CWE-125] (Out-of-Bounds Read), triggered when an integer wrap or wraparound condition drives a read past intended buffer boundaries. Exploitation requires no user interaction and no privileges, but the attacker must reside on the same logical or physical network segment as the vulnerable server. Successful exploitation exposes process memory that may contain lease data, configuration values, or other DHCP state information.
Critical Impact
An unauthenticated attacker on an adjacent network can trigger an integer underflow in the Windows DHCP Server, causing an out-of-bounds read that discloses server memory contents.
Affected Products
- Windows DHCP Server (Microsoft)
- Refer to the Microsoft CVE-2026-62715 Advisory for the definitive list of affected Windows Server builds
Discovery Timeline
- 2026-08-11 - CVE-2026-62715 published to the National Vulnerability Database
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-62715
Vulnerability Analysis
The vulnerability resides in the Windows DHCP Server service, which processes DHCP client requests such as DHCPDISCOVER, DHCPREQUEST, and vendor-specific option payloads. An attacker crafts a malformed DHCP message that causes a length or offset calculation inside the server to underflow. The underflowed value is then used as a size or index parameter for a subsequent read operation. Because the arithmetic wraps to a very large unsigned value, the server reads memory beyond the intended packet buffer. The out-of-bounds bytes are returned to the attacker inside a DHCP response or otherwise leaked through the service's observable behavior. Repeated queries can be used to progressively map process memory. The bug is scoped to information disclosure only; integrity and availability are not directly affected according to the vector CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
Root Cause
The root cause is unchecked arithmetic on an attacker-controlled length or offset field within DHCP option parsing. When the field is smaller than a subtracted header or padding constant, the result wraps below zero and is reinterpreted as a large positive integer. Downstream code trusts this value and performs an out-of-bounds read [CWE-125].
Attack Vector
Exploitation requires network adjacency, meaning the attacker must be on the same broadcast domain or a directly reachable network segment where the DHCP Server accepts client traffic. No authentication or user interaction is required. The attacker sends specially crafted DHCP packets to UDP port 67 and observes responses returned to the client MAC or unicast address. See the Microsoft CVE-2026-62715 Advisory for exact protocol conditions.
No verified public proof-of-concept is available at the time of publication. The vulnerability mechanism is described in prose because no vetted exploit code has been released.
Detection Methods for CVE-2026-62715
Indicators of Compromise
- DHCP request packets on UDP 67 containing malformed option length fields or truncated option payloads that do not match the standard DHCP option TLV structure.
- Unusual volumes of DHCP traffic originating from a single MAC address or spoofed client identifiers on a single VLAN.
- DHCP Server responses of anomalous size or containing option data inconsistent with server configuration.
Detection Strategies
- Deploy network-based DHCP protocol validation to flag option fields where the declared length does not match the remaining packet length.
- Correlate Windows Event Log entries for the DHCP Server service (Microsoft-Windows-DHCP-Server) with packet-level telemetry to spot parsing errors or service restarts.
- Baseline DHCP client behavior per VLAN and alert on clients issuing high-frequency or malformed requests.
Monitoring Recommendations
- Capture DHCP traffic at the distribution layer for retrospective analysis when new indicators are published.
- Monitor for repeated DHCP transactions from clients that never complete a full lease handshake, which can indicate probing.
- Track DHCP Server process memory and CPU metrics for anomalies that may accompany crafted request bursts.
How to Mitigate CVE-2026-62715
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-62715 Advisory to all Windows Server instances running the DHCP Server role.
- Inventory DHCP Server deployments and prioritize patching for servers reachable from user, guest, or IoT VLANs.
- Restrict DHCP Server exposure to trusted network segments using switch-level DHCP snooping and port ACLs.
Patch Information
Microsoft has issued a security update for the Windows DHCP Server service. Consult the Microsoft CVE-2026-62715 Advisory for the KB article numbers, affected Windows Server versions, and build numbers that remediate the integer underflow in DHCP option parsing.
Workarounds
- Enable DHCP snooping on managed switches to drop DHCP traffic from untrusted ports and rate-limit DHCP requests per port.
- Segment DHCP Server infrastructure so that only authorized relay agents and trusted client VLANs can reach UDP port 67.
- Where feasible, use DHCP relay with strict Option 82 validation to reduce direct client access to the server.
No verified configuration snippets are available in the advisory. Refer to the vendor guidance for supported hardening steps.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
