CVE-2022-27615 in DNS Server
Summary
by MITRE • 07/28/2022
Improper limitation of a pathname to a restricted directory ('Path Traversal') vulnerability in cgi component in Synology DNS Server before 2.2.2-5027 allows remote authenticated users to delete arbitrary files via unspecified vectors.
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Analysis
by VulDB Data Team • 08/28/2022
The CVE-2022-27615 vulnerability represents a critical path traversal flaw within the cgi component of Synology DNS Server software, affecting versions prior to 2.2.2-5027. This vulnerability falls under the common weakness enumeration CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory. The flaw enables remote authenticated attackers to exploit the system's file handling mechanisms and execute unauthorized file deletion operations across arbitrary locations within the filesystem. The vulnerability's impact is particularly severe because it allows attackers with valid credentials to bypass normal access controls and potentially compromise the integrity of the entire DNS server infrastructure. The unspecified vectors mentioned in the description suggest that the attack surface may encompass multiple entry points or methods of exploitation within the cgi component's file processing logic.
The technical implementation of this vulnerability stems from inadequate input validation and path sanitization within the DNS server's cgi modules. When authenticated users submit requests through the web interface or api endpoints, the system fails to properly validate or sanitize the file paths used in deletion operations. This allows attackers to craft malicious requests that manipulate the intended file paths to traverse beyond the designated restricted directories. The flaw likely exists in how the system resolves relative paths or handles user-supplied file references, enabling attackers to construct malicious path sequences that bypass directory restrictions. The cgi component's lack of proper path validation creates a scenario where legitimate administrative functions can be subverted to perform unauthorized destructive operations, making this a particularly dangerous privilege escalation vector.
Operationally, this vulnerability presents significant risks to network infrastructure security, especially in environments where Synology DNS Server serves as a critical component of domain name resolution services. Remote authenticated attackers who gain access to legitimate user accounts or administrative credentials can exploit this flaw to delete critical system files, configuration data, or log files, potentially leading to complete service disruption or system compromise. The impact extends beyond simple file deletion, as attackers could target configuration files that control DNS server behavior, leading to denial of service conditions or potential redirection of network traffic. The vulnerability's remote nature means that attackers do not require physical access to the system, making it particularly dangerous in cloud environments or networked deployments where the DNS server is exposed to external networks.
Organizations affected by this vulnerability should immediately implement comprehensive mitigation strategies including mandatory firmware updates to version 2.2.2-5027 or later, which contain the necessary patches to address the path traversal flaw. Network segmentation and access controls should be reinforced to limit the number of authenticated users with administrative privileges, implementing the principle of least privilege. Regular monitoring of system logs for unusual file deletion patterns or unauthorized access attempts should be enabled, with security information and event management systems configured to detect potential exploitation attempts. Additionally, implementing web application firewalls and input validation controls can provide additional layers of protection against similar vulnerabilities in the cgi components of network services. The vulnerability aligns with ATT&CK technique T1059.007 for command and control communications and T1486 for data encryption for ransomware, as exploitation could lead to service disruption and potential data loss scenarios that may require system restoration from backups or complete reinstallation of affected systems.