CVE-2017-11779 in Windows
Summary
by MITRE
The Microsoft Windows Domain Name System (DNS) DNSAPI.dll on Microsoft Windows 8.1, Windows Server 2012 R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows a remote code execution vulnerability when it fails to properly handle DNS responses, aka "Windows DNSAPI Remote Code Execution Vulnerability".
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Analysis
by VulDB Data Team • 01/16/2021
The vulnerability identified as CVE-2017-11779 represents a critical remote code execution flaw within Microsoft Windows Domain Name System DNSAPI.dll component. This weakness affects multiple Windows operating system versions including Windows 8.1, Windows Server 2012 R2, Windows RT 8.1, various Windows 10 releases, and Windows Server 2016. The vulnerability stems from improper handling of DNS responses by the DNSAPI.dll module, creating a pathway for malicious actors to execute arbitrary code on affected systems. The flaw specifically manifests when the DNS client processes malformed or specially crafted DNS responses that the system fails to validate properly. This vulnerability is particularly concerning as it operates at the core of network name resolution functionality that is fundamental to Windows operating systems and network communications.
The technical exploitation of this vulnerability occurs through a buffer overflow or memory corruption issue within the DNSAPI.dll library when processing certain DNS response packets. Attackers can craft malicious DNS responses that, when processed by an affected Windows system, cause the DNS client to improperly handle memory allocation and data processing. This improper handling creates an opportunity for remote code execution without requiring authentication or elevated privileges. The vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1071.004 for application layer protocol: DNS. The flaw essentially allows an attacker to inject malicious code into the DNS client process, potentially leading to complete system compromise and persistent access to the affected network environment.
The operational impact of CVE-2017-11779 extends beyond individual system compromise to encompass broader network security implications. Organizations running affected Windows versions face significant risk as this vulnerability can be exploited remotely through DNS servers, potentially allowing attackers to gain unauthorized access to internal networks. The vulnerability affects systems that rely on standard DNS resolution processes, making it particularly dangerous in enterprise environments where DNS infrastructure is critical for network operations. Once exploited, attackers can establish persistent backdoors, escalate privileges, and move laterally within networks, potentially compromising multiple systems. The widespread nature of affected Windows versions means that organizations across various industries, from government agencies to financial institutions, could be at risk, creating substantial business continuity and security concerns.
Mitigation strategies for this vulnerability require immediate patch deployment through Microsoft's security updates, specifically addressing the DNSAPI.dll handling of DNS responses. Organizations should implement network segmentation and DNS server hardening measures to reduce attack surface, including configuring DNS servers to validate response data more rigorously. Network monitoring solutions should be enhanced to detect anomalous DNS traffic patterns that might indicate exploitation attempts. Additionally, implementing DNS sinkholing and DNS tunneling detection mechanisms can help identify malicious DNS activities. Security teams should also consider disabling unnecessary DNS client functionality and implementing strict firewall rules that limit DNS traffic to trusted servers. The vulnerability demonstrates the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that protect against both known and emerging threats in network infrastructure components.