CVE-2017-16100 in Dns-sync
Summary
by MITRE
dns-sync is a sync/blocking dns resolver. If untrusted user input is allowed into the resolve() method then command injection is possible.
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Analysis
by VulDB Data Team • 02/15/2020
The vulnerability identified as CVE-2017-16100 affects dns-sync, a synchronization and blocking DNS resolver implementation that serves as a middleware component in network security infrastructures. This tool operates by resolving domain names and can be configured to block certain domains based on predefined policies. The vulnerability stems from insufficient input validation within the resolve() method, creating a critical security flaw that allows attackers to inject malicious commands through crafted DNS queries. The affected system processes user-provided domain names without proper sanitization, enabling arbitrary command execution when the resolver handles untrusted input from external sources.
This vulnerability represents a classic command injection flaw classified under CWE-77, which occurs when a program constructs command strings using externally provided data without proper validation or sanitization. The technical implementation flaw lies in the dns-sync component's failure to properly escape or filter special characters that could be interpreted as shell metacharacters. When an attacker crafts a malicious domain name containing shell injection sequences such as semicolons, pipes, or backticks, the resolve() method processes this input directly without adequate protection mechanisms. The vulnerability affects systems where dns-sync operates as a DNS server or resolver, particularly in environments where it accepts queries from untrusted networks or applications.
The operational impact of this vulnerability is severe and can result in complete system compromise. An attacker who successfully exploits this command injection vulnerability gains the ability to execute arbitrary commands with the privileges of the dns-sync process, which typically runs with elevated permissions to manage network traffic and DNS resolution. This could enable attackers to install backdoors, exfiltrate sensitive data, modify DNS records, or disrupt network services. The vulnerability is particularly dangerous in enterprise environments where dns-sync might be deployed as part of network security infrastructure, as it could allow attackers to bypass DNS-based access controls and potentially gain lateral movement within the network. The attack surface extends to any system where dns-sync is configured to accept external queries or where it interfaces with untrusted DNS resolvers.
Mitigation strategies for this vulnerability require immediate implementation of input validation and sanitization measures. Organizations should ensure that all user-provided data passed to the resolve() method undergoes strict validation and filtering to prevent command injection attempts. The recommended approach includes implementing proper escaping of special shell characters, using parameterized command execution where possible, and restricting the execution environment to minimize privilege levels. Security patches should be applied immediately to update dns-sync to versions that address the input validation shortcomings. Network segmentation and access control measures should be implemented to limit which systems can submit queries to the dns-sync service, reducing the attack surface. Additionally, monitoring and logging should be enhanced to detect anomalous DNS query patterns that might indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically shell scripting, and represents a critical weakness that requires immediate remediation to prevent potential system compromise and data breach scenarios.