CVE-2026-45602 Overview
CVE-2026-45602 is a network-exploitable vulnerability in Windows DHCP Server that allows an unauthorized attacker to perform tampering operations across a network. The flaw is classified under [CWE-229] (Improper Handling of Values) and affects the Dynamic Host Configuration Protocol (DHCP) service implementation on Windows. Microsoft published the advisory in its security update guide, and the issue was added to the National Vulnerability Database in June 2026. No authentication or user interaction is required to exploit the vulnerability, and it can be triggered remotely. The combination of high confidentiality and integrity impact, with no required privileges, makes this a priority patching target for environments running Windows DHCP Server roles.
Critical Impact
An unauthenticated attacker with network access to a Windows DHCP Server can tamper with DHCP processing, exposing sensitive configuration data and compromising the integrity of network address assignments.
Affected Products
- Windows DHCP Server (specific versions not enumerated in the NVD entry)
- Refer to the Microsoft CVE-2026-45602 Update Guide for the authoritative list of affected Windows Server builds
Discovery Timeline
- 2026-06-09 - CVE-2026-45602 published to the National Vulnerability Database
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-45602
Vulnerability Analysis
The vulnerability resides in the Windows DHCP Server service, which is responsible for assigning IP addresses and distributing network configuration to clients. According to Microsoft's advisory, the flaw allows an unauthorized attacker to perform tampering operations over a network. The weakness is categorized as [CWE-229] (Improper Handling of Values), indicating the service does not properly process or validate certain input values during DHCP message handling. Successful exploitation impacts both confidentiality and integrity of DHCP operations, though availability is not affected. The attack can be executed remotely without authentication or user interaction, lowering the bar for adversaries operating inside a routable network segment.
Root Cause
The root cause centers on improper handling of values within the DHCP protocol parsing or option processing logic. When the server receives a malformed or unexpected value, it fails to apply the validation required to keep state consistent. This permits an attacker to influence server behavior beyond intended protocol boundaries. Microsoft has not published low-level technical details, so administrators should treat the vendor advisory as authoritative.
Attack Vector
The attack vector is network-based. An adversary sends crafted DHCP traffic to a vulnerable Windows DHCP Server. Because DHCP traffic typically traverses broadcast and unicast paths on internal networks, any attacker with a foothold on a segment that can reach the DHCP service is positioned to attempt exploitation. No credentials or user interaction are required. The vulnerability has not been observed in the wild and is not listed in the CISA Known Exploited Vulnerabilities catalog at the time of publication.
No verified proof-of-concept code is publicly available. Refer to the Microsoft CVE-2026-45602 Update Guide for technical context as Microsoft releases additional details.
Detection Methods for CVE-2026-45602
Indicators of Compromise
- Unexpected modifications to DHCP scope, reservation, or option configurations on Windows DHCP servers
- Anomalous DHCP traffic patterns, including malformed DHCP messages or unusual option fields targeting dhcpserver.exe
- Lease assignments that do not correspond to authorized client requests or that originate from unexpected sources
Detection Strategies
- Monitor the Windows DHCP server operational and admin event logs under Microsoft-Windows-Dhcp-Server for unusual error patterns or repeated parsing failures
- Inspect network captures for DHCP packets that deviate from RFC 2131 structure, particularly oversized or malformed options
- Correlate DHCP audit logs with Active Directory and DNS changes to identify tampering chains that follow successful exploitation
Monitoring Recommendations
- Enable DHCP audit logging on all Windows DHCP servers and forward logs to a centralized analytics platform
- Baseline normal DHCP message rates and option distributions, then alert on statistically significant deviations
- Track configuration changes to DHCP scopes, policies, and server options using change-detection tooling
How to Mitigate CVE-2026-45602
Immediate Actions Required
- Apply the Microsoft security update referenced in the CVE-2026-45602 Update Guide to all Windows DHCP servers
- Inventory all hosts running the DHCP Server role, including legacy and isolated systems, to ensure complete patch coverage
- Restrict network reachability to UDP ports 67 and 68 so that only authorized clients and relay agents can communicate with DHCP servers
Patch Information
Microsoft has published the patch through its standard update channels. Administrators should consult the Microsoft CVE-2026-45602 Update Guide for the specific KB articles and build numbers that address this vulnerability on each supported Windows Server release.
Workarounds
- Segment DHCP servers onto management VLANs and apply access control lists that limit DHCP traffic to trusted relay agents and client subnets
- Enable DHCP server authorization in Active Directory to prevent rogue or unauthorized DHCP services from participating in the network
- Consider temporarily failing over to a patched secondary DHCP server while updates are validated on the primary
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
