CVE-2026-69803 in Windows
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Windows DHCP Server allows an unauthorized attacker to disclose information 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 service represents a critical memory safety flaw that compromises the confidentiality of system data on affected Windows operating systems. This specific defect occurs when the DHCP server processes specially crafted network packets, leading to a scenario where the application attempts to access memory locations beyond the intended buffer boundaries. Because this is an out-of-bounds read rather than a write operation, the primary consequence is not immediate code execution or system instability in the traditional sense of crashes, but rather the unauthorized disclosure of sensitive information stored in adjacent memory regions. An attacker who can reach the vulnerable DHCP server over a network connection can exploit this flaw to leak internal data structures, potentially revealing cryptographic keys, session tokens, or other confidential details that were not intended for external exposure.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-125, which describes Out-of-bounds Read. The root cause typically stems from insufficient validation of input parameters during the parsing of DHCP message fields. When the server receives a packet with malformed or excessively long headers and options, it may calculate an incorrect memory offset based on flawed logic, resulting in reading data outside the allocated buffer space. This behavior is particularly dangerous because modern operating systems employ various mitigations such as Address Space Layout Randomization (ASLR) to protect against exploitation for code execution; however, these protections are less effective at preventing information disclosure through read-only access violations unless additional hardening measures like Data Execution Prevention (DEP) or Control Flow Guard (CFG) inadvertently trigger exceptions that can be leveraged in complex attack chains.
The operational impact of this vulnerability is significant due to the ubiquitous nature of DHCP services within enterprise networks. Since DHCP servers are fundamental infrastructure components responsible for assigning IP addresses and network configuration parameters, they are often exposed on internal subnets accessible by a wide range of devices. An unauthorized attacker positioned on the same local area network segment can send crafted packets to trigger this flaw repeatedly or in specific sequences to extract meaningful data over time. This capability allows adversaries to perform reconnaissance activities with high precision, gathering intelligence that facilitates further lateral movement within the environment. The ability to disclose information without leaving obvious traces of system crashes makes this a stealthy vector for initial access and subsequent privilege escalation campaigns.
In terms of threat actor behavior, exploitation of this vulnerability corresponds to techniques found in the MITRE ATT&CK framework, specifically under Information Collection such as Network Service Discovery or Data from Local System, depending on what specific memory regions are exposed. Attackers may use this information leak to identify running services, extract credentials stored in memory, or gather network topology details that aid in mapping out the attack surface for more destructive exploits like remote code execution via other vulnerabilities. The presence of such a flaw indicates a gap in input sanitization protocols within the DHCP service implementation, highlighting the need for rigorous security testing and adherence to secure coding standards during software development lifecycles.
To mitigate this risk, organizations must ensure that all Windows systems running the DHCP Server role are updated with the latest cumulative updates provided by Microsoft. These patches typically include code changes that enforce stricter bounds checking on input data before processing occurs within the service logic. Administrators should also consider network segmentation strategies to restrict access to DHCP servers from untrusted or public-facing networks, limiting the attack surface available to potential adversaries. Additionally, deploying intrusion detection systems capable of identifying anomalous packet patterns associated with buffer overflow attempts can provide an additional layer of defense against exploitation attempts while patching efforts are underway across the infrastructure.