CVE-2026-77887 in Windows
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Windows DHCP Server allows an authorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a critical out-of-bounds read flaw within the Dynamic Host Configuration Protocol (DHCP) server service on Microsoft Windows operating systems. This specific memory safety error occurs when the DHCP server processes specially crafted network packets or internal data structures that exceed expected boundaries, leading to an attempt to access memory locations outside the allocated buffer space. While traditional out-of-bounds reads are often associated with information disclosure vulnerabilities where sensitive data might be leaked to an attacker, in this particular instance, the nature of the flaw within the DHCP server's processing logic allows for a more severe outcome. The vulnerability stems from improper validation of input parameters or packet structures before they are processed by the core service routines, creating a scenario where memory corruption can occur under specific conditions that trigger arbitrary code execution rather than simple data leakage.
From an operational perspective, this flaw poses a significant risk to network infrastructure stability and security. Because the DHCP server is responsible for assigning IP addresses and other configuration parameters to devices on a local area network, it runs with high privileges as part of the system's core networking stack. An authorized attacker who has valid credentials on the affected Windows host can exploit this memory corruption flaw during the processing of DHCP messages. By crafting malicious packets that trigger the out-of-bounds read condition in a precise manner, the attacker can manipulate the execution flow of the process. This manipulation allows for the injection and subsequent execution of arbitrary code within the context of the privileged system account running the DHCP service. Consequently, this leads to local privilege escalation or full remote control if combined with other vectors, effectively compromising the integrity and confidentiality of the entire network segment managed by that server.
The technical classification of this vulnerability aligns closely with CWE-125, which defines out-of-bounds read errors where software reads data past the end or before the beginning of a buffer. However, due to the specific exploitation path leading to code execution, it also exhibits characteristics often associated with memory corruption vulnerabilities that can be leveraged for arbitrary code execution, similar in impact profile to certain heap-based overflow scenarios found in ATT&CK technique T1203, which covers Exploitation for Client Execution. The attack vector typically involves the attacker sending a specially crafted DHCP request or response packet to the vulnerable server. Since the vulnerability requires an authorized attacker, it implies that network-level access and valid authentication credentials are prerequisites, placing this threat within the context of insider threats or compromised user accounts rather than unauthenticated remote exploitation.
Mitigation strategies for this vulnerability primarily involve applying the relevant security patches released by Microsoft as part of their monthly cumulative update cycle. Administrators should ensure that all Windows DHCP servers are updated to versions that include fixes for this specific memory safety issue. In addition to patching, network segmentation and strict access control lists can help limit exposure by restricting which hosts can communicate with the DHCP server on UDP ports 67 and 68. Monitoring logs for unusual patterns in DHCP traffic or unexpected process behavior may also aid in early detection of exploitation attempts. Furthermore, implementing least privilege principles ensures that even if an attacker gains initial foothold through other means, their ability to interact directly with the DHCP service is minimized, thereby reducing the attack surface available for exploiting this specific out-of-bounds read flaw.