CVE-2019-5476 in Lookup-Server
Summary
by MITRE
An SQL Injection in the Nextcloud Lookup-Server < v0.3.0 (running on https://lookup.nextcloud.com) caused unauthenticated users to be able to execute arbitrary SQL commands.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 11/21/2023
The vulnerability CVE-2019-5476 represents a critical SQL injection flaw in Nextcloud's Lookup-Server component prior to version 0.3.0. This vulnerability was exposed through the public endpoint at https://lookup.nextcloud.com and allowed unauthenticated attackers to execute arbitrary SQL commands against the underlying database. The issue stems from inadequate input validation and sanitization within the server's query processing logic, creating a direct pathway for malicious SQL code execution. The vulnerability affects the core functionality of Nextcloud's contact lookup service, which is designed to provide federated contact discovery across different Nextcloud instances.
The technical exploitation of this vulnerability occurs through improper handling of user-supplied input parameters in the lookup server's database queries. When unauthenticated users submit crafted requests to the lookup endpoint, the server fails to properly escape or parameterize the input before incorporating it into SQL statements. This classic SQL injection pattern allows attackers to manipulate the database query structure and execute arbitrary commands with the privileges of the database user account. The vulnerability maps directly to CWE-89 which defines SQL injection as the insertion of malicious SQL code into input fields for execution by the database. The attack vector specifically targets the lookup server's API endpoints that process contact information queries from federated Nextcloud instances.
The operational impact of this vulnerability is severe and multifaceted. Unauthenticated attackers could gain read access to sensitive contact data, potentially including personal information from millions of Nextcloud users. The vulnerability also allows for data modification and deletion operations, potentially compromising the integrity of the contact database. Additionally, attackers could leverage this vulnerability to escalate privileges or perform further reconnaissance on the underlying infrastructure. The exposed endpoint at https://lookup.nextcloud.com served as a public interface that was particularly dangerous because it required no authentication credentials, making the attack surface extremely broad and accessible to any internet user. This vulnerability directly aligns with ATT&CK technique T1213.002 which covers data from information repositories, and T1071.004 which covers application layer protocol: DNS, both of which are relevant to the exploitation of federated contact lookup services.
Mitigation strategies for CVE-2019-5476 require immediate patching of the Nextcloud Lookup-Server to version 0.3.0 or later, which includes proper input validation and parameterized query execution. Organizations should implement network segmentation to limit access to the lookup server endpoint and deploy web application firewalls to detect and block malicious SQL injection attempts. Database access controls should be reviewed to ensure least privilege principles are applied, and input sanitization should be implemented at multiple layers of the application stack. Regular security audits and penetration testing of federated services should be conducted to identify similar vulnerabilities. The fix addresses the root cause by implementing proper parameterized queries and input validation, which prevents malicious SQL code from being executed within the database context. Organizations using Nextcloud should also monitor for similar vulnerabilities in other federated services and maintain updated threat intelligence to prevent exploitation of related attack patterns.