CVE-2019-3999 in inSync Windows Client
Summary
by MITRE
Improper neutralization of special elements used in an OS command in Druva inSync Windows Client 6.5.0 allows a local, unauthenticated attacker to execute arbitrary operating system commands with SYSTEM privileges.
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Analysis
by VulDB Data Team • 10/17/2025
The vulnerability identified as CVE-2019-3999 represents a critical command injection flaw within the Druva inSync Windows Client version 6.5.0 that fundamentally compromises system security through improper handling of operating system commands. This issue arises from inadequate sanitization of user-supplied input that subsequently gets processed through operating system command execution mechanisms, creating a pathway for malicious actors to escalate privileges and execute arbitrary code with SYSTEM level access. The flaw specifically manifests in the client software's handling of special elements within OS command contexts, where input validation and sanitization processes fail to properly neutralize potentially dangerous characters or sequences that could be interpreted by the underlying operating system as command delimiters or execution directives.
The technical implementation of this vulnerability stems from the Windows client's failure to properly sanitize input parameters before incorporating them into system command execution flows. When the inSync client processes certain user-provided data, it directly incorporates this unvalidated input into OS command strings without adequate neutralization of special characters such as semicolons, pipes, or other command separators that could alter the intended execution flow. This improper neutralization pattern aligns with CWE-77 and CWE-88 categories, which specifically address command injection vulnerabilities where user-controllable data is improperly integrated into command execution contexts. The vulnerability operates at the intersection of input validation failures and privilege escalation, as the local attacker can leverage this flaw to execute commands with the highest available privileges on the target system, effectively bypassing standard user access controls and security boundaries.
From an operational impact perspective, this vulnerability enables a local, unauthenticated attacker to achieve complete system compromise without requiring any authentication credentials or network access. The ability to execute arbitrary commands with SYSTEM privileges means that the attacker can modify system files, install malicious software, establish persistent backdoors, access sensitive data, and potentially escalate to domain administrator privileges if the compromised system is part of a larger network infrastructure. The attack vector is particularly concerning because it requires no network connectivity, no user interaction, and no authentication, making it highly exploitable in environments where physical access to systems is possible. This vulnerability essentially provides an attacker with a powerful foothold that can be leveraged for lateral movement, data exfiltration, and long-term persistence within the target environment.
The exploitation of this vulnerability aligns with several ATT&CK framework techniques including T1059 for command and script execution, T1068 for exploit for privilege escalation, and T1078 for valid accounts. Security professionals should note that this flaw represents a significant risk to organizations relying on Druva inSync for data protection, as it undermines the very security controls the software is designed to provide. The vulnerability's impact extends beyond immediate command execution to encompass potential data loss, system integrity compromise, and regulatory compliance violations, particularly in environments governed by standards such as SOC 2, HIPAA, or PCI DSS where unauthorized system access constitutes a serious security incident. Organizations should prioritize immediate remediation through vendor-provided patches and consider implementing additional monitoring for suspicious command execution patterns and privilege escalation attempts.
Mitigation strategies should include immediate deployment of the vendor-supplied security patch for Druva inSync version 6.5.0, along with comprehensive network monitoring to detect unauthorized command execution attempts. System administrators should implement principle of least privilege controls, regularly audit system access logs, and establish robust endpoint detection and response capabilities to identify potential exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments to identify other potentially affected systems and implement network segmentation to limit the impact of successful exploitation attempts. The remediation process should also include regular security awareness training for personnel who may inadvertently provide access to systems where this vulnerability could be exploited, as well as maintaining updated threat intelligence feeds to monitor for related attack patterns and indicators of compromise.