CVE-2026-77501 in Windows
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Windows DHCP Server allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an out-of-bounds read within the Microsoft Dynamic Host Configuration Protocol (DHCP) server represents a critical memory safety flaw that compromises the availability of network infrastructure services. This specific defect occurs when the DHCP server processes specially crafted packets or malformed data structures, leading to a scenario where the application attempts to access memory locations beyond the intended buffer boundaries. Unlike out-of-bounds writes which can often lead to code execution, an out-of-bounds read primarily impacts system stability and service continuity by causing the application to crash or behave unpredictably when it encounters invalid memory addresses during packet parsing operations.
From a technical perspective, this flaw is rooted in improper validation of input data lengths relative to allocated buffer sizes within the DHCP server component. When the server receives network traffic that triggers this specific code path, it fails to correctly verify whether the requested read operation stays within the confines of the pre-allocated memory space. This lack of rigorous boundary checking allows an attacker who can send packets to the vulnerable service to induce a denial-of-service condition. The impact is immediate and severe for organizations relying on DHCP for IP address management, as the crash or instability of the server disrupts network connectivity for clients attempting to obtain or renew IP configurations.
The operational impact of this vulnerability extends beyond simple downtime; it affects the reliability of core networking services that are foundational to most enterprise environments. An unauthorized attacker positioned within the same network segment can exploit this flaw by sending a single malicious packet, causing the DHCP server service to stop responding. This results in a complete denial of service for all devices dependent on that specific server for network access. In larger deployments where multiple servers share responsibilities or rely on synchronized databases, such an incident could trigger cascading failures if high-availability mechanisms are not properly configured and tested against this specific attack vector.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-125, which describes out-of-bounds read errors that allow attackers to read sensitive memory contents or cause crashes through invalid access patterns. In the context of the MITRE ATT&CK framework, this exploitation technique falls under Tactic TA0004 Impact and specifically Technique T1499 Endpoint Denial of Service, as it aims to degrade or eliminate the capacity of a computing resource by exhausting system resources or causing application crashes through malicious input rather than exploiting privilege escalation paths.
Mitigation strategies for this vulnerability prioritize immediate patching via official Microsoft security updates that address the memory validation logic within the DHCP server component. Administrators should ensure that all Windows servers running the DHCP role are updated to versions containing the specific fix for this out-of-bounds read issue. In environments where patching is not immediately feasible, network segmentation and firewall rules can be employed to restrict access to the DHCP service ports from untrusted or external networks, thereby limiting the attack surface available to potential adversaries until a permanent remediation can be applied.