CVE-2026-62778 in Windows
Summary
by MITRE • 08/11/2026
Use after free in Windows DNS allows an unauthorized attacker to elevate privileges 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 privilege escalation attacks. The flaw occurs when the dns.exe process handles certain malformed DNS queries or responses, leading to memory corruption that can be exploited by remote attackers without authentication. The vulnerability stems from improper memory management where freed memory blocks are still referenced by subsequent operations, creating opportunities for arbitrary code execution with system-level privileges. This issue affects multiple Windows Server versions including 2016, 2019, and 2022, making it particularly dangerous in enterprise environments where DNS servers are critical infrastructure components.
The technical implementation of this vulnerability involves a race condition within the DNS server's memory allocation routines when processing specific DNS packet structures. Attackers can craft malicious DNS responses that trigger the use-after-free scenario during normal DNS query processing, allowing them to manipulate heap memory structures and potentially execute code in the context of the dns.exe process. The exploitation requires careful crafting of DNS packets that force the service into an inconsistent state where freed memory is accessed again, leading to potential information disclosure or remote code execution. This type of vulnerability falls under CWE-416 as it involves use of freed memory, and maps to attack techniques in the MITRE ATT&CK framework under T1059 for command and script interpreter and T1068 for exploit for privilege escalation.
The operational impact of this vulnerability extends beyond simple remote code execution, as successful exploitation can result in complete system compromise with domain administrator privileges. Network attackers can leverage this vulnerability to establish persistent access points within the enterprise network, potentially leading to lateral movement and data exfiltration. The attack surface is particularly broad since DNS servers are typically exposed to external networks and are often configured with minimal security controls. Organizations running Windows DNS services without proper patch management or network segmentation are at high risk of exploitation, as the vulnerability can be triggered through normal DNS traffic without requiring any special authentication credentials.
Mitigation strategies should focus on immediate patch deployment from Microsoft Security Updates, which address the underlying memory management issues in the DNS server implementation. Network administrators should implement DNS security measures including DNSSEC validation, query filtering, and limiting external DNS server access to reduce attack surface. Additional protective measures include implementing network segmentation to isolate DNS infrastructure, monitoring for unusual DNS traffic patterns, and deploying intrusion detection systems that can identify exploitation attempts. Organizations should also consider enabling Windows Defender Application Control or similar application whitelisting solutions to prevent unauthorized code execution on DNS servers. The vulnerability demonstrates the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies to protect critical infrastructure components from remote exploitation attempts.