CVE-2020-35970 in YzmCMS
Summary
by MITRE • 06/04/2021
An issue was discovered in YzmCMS 5.8. There is a SSRF vulnerability in the background collection management that allows arbitrary file read.
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Analysis
by VulDB Data Team • 06/07/2021
The vulnerability CVE-2020-35970 represents a critical server-side request forgery flaw in YzmCMS version 5.8 that resides within the background collection management module. This vulnerability stems from insufficient input validation and sanitization mechanisms that fail to properly restrict user-supplied URLs or endpoints during the content collection process. The flaw allows authenticated attackers with access to the administrative interface to manipulate the system into making unintended requests to internal or external resources, potentially enabling unauthorized data access and system reconnaissance activities.
The technical implementation of this vulnerability demonstrates a classic SSRF weakness where the application fails to adequately validate and sanitize URL parameters used in the collection management functionality. When administrators or authorized users interact with the content collection features, the system processes user-provided URLs without proper restrictions on protocol schemes or destination addresses. This allows malicious actors to craft specially formatted requests that can bypass normal network security controls and potentially access internal systems or sensitive files that should remain protected. The vulnerability is particularly concerning because it exists within the administrative backend where legitimate users already possess elevated privileges, making the attack surface more dangerous.
The operational impact of this vulnerability extends beyond simple data leakage, as it provides potential attackers with the capability to perform internal network reconnaissance and access restricted resources. An attacker could leverage this flaw to read local files on the server, access internal services that are not exposed to the public internet, or even attempt to exploit other vulnerabilities within the internal network. The arbitrary file read capability specifically enables attackers to extract configuration files, database credentials, application source code, and other sensitive information that could lead to further compromise of the affected system. This vulnerability aligns with CWE-918, which categorizes server-side request forgery vulnerabilities, and represents a significant risk to the confidentiality and integrity of the CMS platform.
Mitigation strategies for CVE-2020-35970 should focus on implementing strict input validation and URL sanitization within the collection management module. Organizations should ensure that all user-supplied URLs are validated against a whitelist of approved protocols and domains, with particular attention to preventing access to internal network addresses and local file systems. The recommended approach includes implementing proper protocol filtering to restrict requests to http and https schemes only, while blocking access to loopback addresses, private IP ranges, and file:// protocols. Additionally, network segmentation and firewall rules should be implemented to limit access to internal services from the CMS application server, following the principle of least privilege as outlined in the NIST Cybersecurity Framework. Regular security updates and patches should be applied to ensure that the CMS remains protected against known vulnerabilities, with continuous monitoring of the system for any unauthorized access attempts or suspicious network activity that could indicate exploitation of this flaw.