CVE-2020-1350 in Windows (SigRed)
Summary
by MITRE
A remote code execution vulnerability exists in Windows Domain Name System servers when they fail to properly handle requests, aka 'Windows DNS Server Remote Code Execution Vulnerability'.
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability identified as CVE-2020-1350 represents a critical remote code execution flaw in Microsoft Windows Domain Name System servers that has significant implications for enterprise network security. This vulnerability specifically affects the DNS server service running on Windows operating systems and can be exploited by remote attackers without authentication. The flaw resides in how the DNS server processes certain malformed requests, creating a condition where malicious input can trigger arbitrary code execution on the affected system. The vulnerability was discovered and disclosed by Microsoft in their security bulletin released in July 2020, and it has been assigned the Common Weakness Enumeration identifier CWE-121, which classifies it as a buffer overflow condition. This weakness occurs when a program writes data beyond the boundaries of a fixed-length buffer, potentially allowing attackers to overwrite adjacent memory locations and execute malicious code.
The technical exploitation of CVE-2020-1350 leverages the DNS server's handling of specific packet formats that cause memory corruption during request processing. When a maliciously crafted DNS query is sent to a vulnerable DNS server, the server fails to properly validate the incoming data structure, leading to a buffer overflow condition. This memory corruption can be manipulated to redirect program execution flow, potentially allowing an attacker to execute arbitrary code with the privileges of the DNS server process. The vulnerability affects Windows Server 2008, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019, and Windows Server 2022 operating systems. The attack surface is particularly concerning because DNS servers are often critical infrastructure components that are accessible from external networks, making them prime targets for exploitation. The vulnerability can be exploited through both UDP and TCP protocols, and the attack requires no authentication, making it particularly dangerous for organizations with exposed DNS servers.
The operational impact of CVE-2020-1350 extends beyond simple code execution, as it can lead to complete system compromise and potential lateral movement within networks. Once an attacker gains remote code execution capability on a DNS server, they can use this foothold to pivot to other systems on the network, potentially compromising additional servers and workstations. The vulnerability can also be used to establish persistent access through the DNS server, as attackers can modify DNS records to redirect traffic or maintain backdoor access. According to the MITRE ATT&CK framework, this vulnerability maps to several techniques including T1071.004 for application layer protocol DNS, T1059.001 for command and scripting interpreter, and T1021.002 for remote services. Organizations that rely heavily on DNS infrastructure for network operations and security controls face the highest risk, as compromising a DNS server can effectively disrupt network operations while providing attackers with elevated privileges. The vulnerability's impact is further amplified by the fact that DNS servers often run with high privileges and may be configured to forward queries to other internal servers, creating additional attack vectors.
Mitigation strategies for CVE-2020-1350 should include immediate deployment of Microsoft security updates, which address the underlying buffer overflow condition in the DNS server implementation. Organizations should also implement network segmentation to limit exposure of DNS servers to untrusted networks, and employ network monitoring to detect unusual DNS query patterns that may indicate exploitation attempts. The use of DNS server hardening techniques, such as disabling unnecessary DNS server features, implementing DNS query logging, and configuring proper access controls, can significantly reduce the attack surface. Additionally, organizations should consider implementing DNS tunneling detection mechanisms and monitoring for anomalous DNS traffic patterns that could indicate exploitation of this vulnerability. The vulnerability also underscores the importance of maintaining up-to-date security patches and implementing robust vulnerability management processes. Network administrators should conduct thorough assessments of their DNS server configurations and ensure that only necessary services are running on these critical infrastructure components. Regular security testing and penetration testing should be performed to identify and remediate similar vulnerabilities before they can be exploited by malicious actors.