CVE-2020-35249 in ElkarBackup
Summary
by MITRE • 11/02/2021
Cross Site Scripting (XSS) vulnerability in ElkarBackup 1.3.3, allows attackers to execute arbitrary code via the name parameter to the add client feature.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/05/2021
The vulnerability CVE-2020-35249 represents a critical cross site scripting flaw identified in ElkarBackup version 1.3.3, a popular open source backup solution designed for enterprise environments. This vulnerability resides within the web interface of the backup management system, specifically in the client addition functionality that allows administrators to register new backup clients. The flaw enables malicious actors to inject malicious scripts into the system through a carefully crafted name parameter, which is processed without proper input sanitization or output encoding mechanisms. The vulnerability affects the core administrative functionality of the backup system, potentially compromising the entire backup infrastructure if exploited successfully.
The technical implementation of this vulnerability stems from insufficient validation and sanitization of user-supplied input within the add client feature. When an attacker submits a malicious payload through the name parameter, the system fails to properly escape or filter special characters that could be interpreted as executable script code. This lack of input validation creates a persistent XSS vector that can be exploited in multiple contexts including reflected and stored XSS scenarios. The vulnerability is particularly concerning because it occurs in a privileged administrative function where attackers could potentially escalate their privileges and gain unauthorized access to backup configurations, sensitive data, or even execute arbitrary commands on the underlying system. This flaw directly maps to CWE-79 which defines the common weakness of cross site scripting in web applications, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with a potential foothold for more sophisticated attacks within the backup environment. An attacker could leverage this vulnerability to steal administrative credentials, modify backup schedules, inject malicious code into backup processes, or even redirect users to phishing sites that could compromise additional systems. The attack surface is particularly dangerous because backup systems often contain sensitive organizational data, making them attractive targets for data exfiltration or ransomware operations. In enterprise environments where ElkarBackup manages critical backup infrastructure, this vulnerability could lead to complete system compromise, data loss, or regulatory compliance violations. The stored nature of the XSS vulnerability means that malicious payloads could persist and affect multiple users over time, amplifying the potential damage.
Mitigation strategies for CVE-2020-35249 should prioritize immediate patching of the ElkarBackup system to version 1.3.4 or later, which contains the necessary input validation fixes. Organizations should implement comprehensive input sanitization at multiple layers including web application firewall rules, proper output encoding for all user-controllable parameters, and regular security scanning of the backup management interface. Network segmentation and least privilege access controls should be enforced to limit the potential impact of exploitation. Additionally, security monitoring should be implemented to detect unusual activities in the backup management interface, and regular security audits should be conducted to identify similar vulnerabilities in other administrative components. The vulnerability highlights the importance of proper secure coding practices including input validation, output encoding, and defense in depth strategies that align with industry standards such as OWASP Top Ten and NIST Cybersecurity Framework.