CVE-2017-4990 in Avamar Server
Summary
by MITRE
In EMC Avamar Server Software 7.4.1-58, 7.4.0-242, 7.3.1-125, 7.3.0-233, 7.3.0-226, an unauthorized attacker may leverage the file upload feature of the system maintenance page to load a maliciously crafted file to any directory which could allow the attacker to execute arbitrary code on the Avamar Server system.
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Analysis
by VulDB Data Team • 12/29/2020
The vulnerability identified as CVE-2017-4990 represents a critical remote code execution flaw within EMC Avamar Server Software across multiple versions including 7.4.1-58, 7.4.0-242, 7.3.1-125, 7.3.0-233, and 7.3.0-226. This security weakness stems from inadequate input validation mechanisms within the system maintenance page functionality, specifically in the file upload component that lacks proper authorization checks and sanitization protocols. The flaw allows an unauthenticated attacker to exploit the file upload feature and place malicious files in any directory accessible by the Avamar Server system, creating a significant attack surface that could be leveraged for system compromise. The vulnerability operates under the Common Weakness Enumeration framework as a weakness categorized under CWE-434, which describes "Unrestricted Upload of File with Dangerous Type," a classification that directly aligns with the exposed file upload functionality that permits arbitrary file placement without proper validation.
The technical implementation of this vulnerability enables an attacker to bypass authentication requirements and directly interact with the system maintenance interface to upload malicious payloads. The affected Avamar Server software does not properly validate file types or enforce directory restrictions during the upload process, allowing attackers to place executable files in critical system directories. This misconfiguration creates a path for privilege escalation and remote code execution, as the uploaded files can be executed with the privileges of the Avamar Server process. The attack vector is particularly concerning because it requires no prior authentication credentials, making it accessible to any remote attacker who can reach the system maintenance page. According to MITRE ATT&CK framework, this vulnerability maps to T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1078.004 for "Valid Accounts: Default Accounts," as attackers could leverage the compromised system to execute commands using PowerShell or other scripting languages. The exploitability of this vulnerability is further enhanced by the fact that the Avamar Server typically runs with elevated privileges, potentially allowing attackers to gain full system control.
The operational impact of CVE-2017-4990 extends beyond simple unauthorized access, as successful exploitation could result in complete system compromise, data exfiltration, and potential lateral movement within network environments. Organizations relying on Avamar Server for data protection and backup operations face significant risk of data loss or corruption, as attackers could modify backup configurations, delete critical data, or install persistent backdoors. The vulnerability affects the core functionality of the Avamar Server, which is designed to protect enterprise data, making it a prime target for threat actors seeking to disrupt business operations or gain access to sensitive information. Network administrators must consider the potential for this vulnerability to serve as a foothold for broader attacks, as compromised Avamar servers often contain access to extensive backup data and may be integrated with enterprise networks. The risk assessment indicates that this vulnerability should be prioritized for immediate remediation, as it provides attackers with a straightforward path to execute arbitrary code on the target system without requiring authentication credentials or specialized knowledge of the system internals. The affected software versions represent widely deployed backup solutions in enterprise environments, increasing the potential attack surface and impact of this vulnerability.
Mitigation strategies for CVE-2017-4990 should focus on immediate patch application from EMC, which would address the underlying file upload validation issues and implement proper authorization checks. Organizations should also implement network segmentation to restrict access to the system maintenance page and limit the attack surface by ensuring that only authorized personnel can reach the vulnerable interface. Additional defensive measures include implementing web application firewalls to monitor and filter file upload requests, deploying intrusion detection systems to identify suspicious upload activities, and conducting regular security audits of system maintenance interfaces. The remediation process should also involve disabling unnecessary administrative interfaces and implementing multi-factor authentication for any remaining access points. Security teams should monitor for exploitation attempts through log analysis and implement proper access controls to prevent unauthorized individuals from reaching the vulnerable system maintenance page. Regular vulnerability assessments and penetration testing should be conducted to identify similar weaknesses in related systems and ensure that the security posture remains robust against evolving threats. The vulnerability demonstrates the importance of proper input validation and authorization controls in enterprise backup systems, highlighting the need for comprehensive security measures that protect critical data infrastructure from remote exploitation attempts.