CVE-2026-65789
Summary
by MITRE • 08/11/2026
Use after free in Windows DNS allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical use-after-free condition in the Windows Domain Name System service that enables remote code execution by unauthorized attackers. The flaw occurs when the dns.exe process handles certain malformed DNS responses or packet structures, leading to memory management errors where freed memory regions are accessed after being reallocated for other purposes. This specific vulnerability falls under the CWE-416 category of Use After Free conditions, which is a well-established class of memory corruption vulnerabilities that have historically led to arbitrary code execution exploits.
The technical implementation involves the DNS server component in Windows operating systems failing to properly validate input parameters when processing DNS queries or responses from external sources. When an attacker crafts malicious DNS packets containing specially formatted resource records or TTL values, the dns.exe process may attempt to access memory locations that have already been freed during previous operations. This creates a scenario where attacker-controlled data can be placed in previously freed memory spaces, allowing for precise control over the execution flow when the freed memory is reallocated and accessed.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a remote exploitation vector that requires no authentication or local access to the target system. Network-based attacks can leverage this flaw by sending malicious DNS responses to Windows DNS servers, potentially compromising entire network infrastructures through lateral movement once initial access is achieved. The vulnerability affects multiple Windows versions including server editions and workstations, making it particularly dangerous in enterprise environments where DNS services are critical infrastructure components.
Security practitioners should implement immediate mitigations including applying Microsoft security patches as soon as they become available, configuring DNS servers to limit external query responses, and implementing network segmentation controls to restrict access to DNS services. The vulnerability aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS, where adversaries use DNS protocols for command and control communications. Additional defensive measures include monitoring for unusual DNS traffic patterns, implementing DNS sinkhole configurations, and deploying network intrusion detection systems that can identify malformed DNS responses characteristic of this exploit.
The root cause stems from insufficient input validation within the Windows DNS processing stack, specifically in how resource record data is handled during memory allocation and deallocation cycles. This represents a classic memory safety issue that demonstrates the importance of proper memory management practices in system-level code. Organizations should conduct thorough vulnerability assessments targeting their DNS infrastructure and implement comprehensive monitoring solutions to detect exploitation attempts before they can succeed in establishing persistent access or executing malicious payloads within their networks.