CVE-2026-62755 in Windows
Summary
by MITRE • 08/11/2026
Stack-based buffer overflow in Windows DHCP Client allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical stack-based buffer overflow within the Windows Dynamic Host Configuration Protocol client component that enables local privilege escalation for authenticated attackers. The flaw exists in how the dhcp client processes certain network configuration data during lease acquisition or renewal operations, specifically when handling malformed or excessively long option values in dhcp messages. The vulnerability manifests when the client attempts to store incoming dhcp options on the stack without proper bounds checking, allowing an attacker with local access to craft malicious dhcp responses that overwrite adjacent stack memory locations.
The technical implementation of this vulnerability aligns with CWE-121 Stack-based Buffer Overflow, where insufficient validation of input data leads to memory corruption that can be exploited to execute arbitrary code. The Windows dhcp client operates with elevated privileges during normal operation to manage network configuration changes, making successful exploitation particularly dangerous as it allows attackers to leverage these privileges for unauthorized system access. The attack vector requires local authentication since the dhcp client must be running and configured to accept network responses, but once exploited, the attacker can gain SYSTEM level privileges through direct memory manipulation.
From an operational perspective, this vulnerability creates a significant risk for enterprise environments where attackers may have gained initial access through other means such as phishing or credential theft. The attack requires minimal network access and can be executed with relatively simple tools that craft dhcp packets with oversized option data. Security controls such as network segmentation and firewall rules may not prevent exploitation since the attack occurs locally on a compromised system, making detection more challenging. Organizations using Windows systems with dhcp client functionality are particularly vulnerable, especially those with multiple network interfaces or systems configured to automatically accept dhcp responses.
Mitigation strategies should focus on both immediate defensive measures and long-term architectural improvements. Microsoft has released security updates that address the buffer overflow through proper input validation and stack canary implementations in the dhcp client component. Organizations should prioritize patch management to ensure all systems receive these updates promptly, particularly those running vulnerable versions of Windows Server or Windows 10/11 client operating systems. Network monitoring solutions should be configured to detect unusual dhcp traffic patterns that might indicate exploitation attempts, though this may not prevent successful attacks. Additionally, implementing least privilege principles for dhcp client processes and disabling unnecessary network interfaces can reduce the attack surface while maintaining operational functionality. The vulnerability also highlights the importance of following secure coding practices in network protocol implementations and aligns with ATT&CK technique T1068 for local privilege escalation through exploitation of system vulnerabilities.