CVE-2026-69929 Overview
CVE-2026-69929 is an out-of-bounds read vulnerability [CWE-125] in the Microsoft Windows Dynamic Host Configuration Protocol (DHCP) Server service. An unauthenticated attacker can send crafted network traffic to a vulnerable DHCP Server and read memory beyond the intended buffer boundary. Successful exploitation results in disclosure of sensitive information from the DHCP Server process address space. The flaw affects a wide range of Windows Server and Windows 10 builds that ship the DHCP Server role. Microsoft published the advisory on September 8, 2026, and rates the issue high severity. No public proof-of-concept, exploit code, or in-the-wild exploitation has been reported.
Critical Impact
A remote, unauthenticated attacker can read memory contents from the Windows DHCP Server process over the network without user interaction, exposing credentials, keys, or configuration data useful for follow-on attacks.
Affected Products
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025 (DHCP Server role)
- Microsoft Windows 10 version 1607 (x64 and x86)
- Microsoft Windows 10 version 1809 (x64 and x86)
Discovery Timeline
- 2026-09-08 - CVE-2026-69929 published to NVD
- 2026-09-10 - Last updated in NVD database
Technical Details for CVE-2026-69929
Vulnerability Analysis
The vulnerability resides in the Windows DHCP Server service, which listens on UDP port 67 and responds to DHCP client requests. Improper bounds checking during parsing of an inbound DHCP message causes the service to read beyond an allocated buffer. The returned or logged data can include adjacent heap contents belonging to the DHCP Server process. Because DHCP Server typically runs with elevated privileges on domain-joined infrastructure, the disclosed bytes may contain lease metadata, cached credentials, or pointers useful for bypassing address space layout randomization (ASLR). The issue is a pure information-disclosure primitive — the confidentiality impact is high while integrity and availability are unaffected. Exploitation is remote, requires no privileges, and needs no user interaction.
Root Cause
The underlying weakness is an out-of-bounds read [CWE-125] triggered during DHCP option or packet-field parsing. The service trusts a length or offset value derived from attacker-controlled packet data and dereferences memory without validating that the read stays within the source buffer. Microsoft has not published implementation-level details in the public advisory.
Attack Vector
An attacker sends a specially crafted DHCP packet to a reachable DHCP Server endpoint. In typical enterprise deployments the DHCP service is exposed on internal networks and relayed across VLANs by DHCP relay agents, extending the reachable attack surface. Any host able to deliver a UDP DHCP request to the server — including compromised workstations, rogue VMs, and unmanaged network devices — can trigger the read. See the Microsoft Security Update Guide for CVE-2026-69929 for vendor-authoritative details.
No public proof-of-concept exploit is available at the time of publication.
Detection Methods for CVE-2026-69929
Indicators of Compromise
- Malformed DHCP DISCOVER, REQUEST, or INFORM packets with inconsistent option-length fields arriving at UDP port 67.
- Unexpected DHCP traffic sourced from hosts that are not legitimate DHCP clients or relay agents.
- Repeated DHCP requests from a single source paired with abnormal option payloads or oversized vendor-class identifiers.
Detection Strategies
- Deploy network intrusion detection signatures that validate DHCP option length fields and flag packets where declared option size exceeds remaining packet bytes.
- Correlate Windows DHCP Server audit logs (%windir%\System32\dhcp\DhcpSrvLog-*.log) with network telemetry to identify anomalous request patterns.
- Hunt for DHCP server process (svchost.exe hosting DHCPServer) crashes or unexpected memory access events in EDR telemetry.
Monitoring Recommendations
- Enable Windows Event logging for the DHCP Server service (Event IDs 1040–1064) and forward events to a centralized analytics platform.
- Baseline normal DHCP client populations per scope and alert on new or unauthorized MAC addresses issuing requests.
- Monitor for abnormal outbound data flows from DHCP servers that could indicate staged exfiltration following successful memory disclosure.
How to Mitigate CVE-2026-69929
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-69929 to all Windows Server hosts running the DHCP Server role.
- Inventory every server with the DHCP Server role installed, including domain controllers and infrastructure servers, and prioritize internet-adjacent or multi-tenant segments first.
- Restrict UDP port 67 traffic at network boundaries and between untrusted VLANs where DHCP relaying is not required.
Patch Information
Microsoft has released updates addressing CVE-2026-69929 across all supported Windows Server and Windows 10 builds listed in the affected products section. Refer to the Microsoft Security Update Guide for the specific KB article numbers that correspond to your operating system version and servicing channel.
Workarounds
- Enable DHCP audit logging and increase the audit log size to preserve forensic evidence if immediate patching is not feasible.
- Enforce Layer 2 controls such as DHCP snooping on managed switches to limit which hosts can transmit DHCP packets to the server.
- Where a Windows host is not required to serve DHCP, stop and disable the DHCPServer service until the update can be applied.
# Check whether the DHCP Server role is installed and enabled (PowerShell)
Get-WindowsFeature -Name DHCP
Get-Service -Name DHCPServer | Select-Object Status, StartType
# Temporarily stop and disable the service if not required
Stop-Service -Name DHCPServer -Force
Set-Service -Name DHCPServer -StartupType Disabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
