CVE-2020-8099 in Antivirus Free
Summary
by MITRE
A vulnerability in the improper handling of junctions in Bitdefender Antivirus Free can allow an unprivileged user to substitute a quarantined file, and restore it to a privileged location. This issue affects: Bitdefender Antivirus Free versions prior to 1.0.17.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2020-8099 represents a critical privilege escalation flaw within Bitdefender Antivirus Free versions prior to 1.0.17. This issue stems from the improper handling of file junctions during the quarantine process, creating a pathway for unprivileged users to manipulate security controls and potentially execute malicious code with elevated privileges. The vulnerability specifically targets the antivirus software's file management system where junction points are not properly validated or secured, allowing attackers to exploit the system's trust model.
The technical flaw manifests through the manipulation of symbolic links or junction points that Bitdefender uses to track quarantined files. When the antivirus software processes quarantined items, it fails to properly validate the integrity of junction points, enabling an attacker to replace the quarantined file with a malicious alternative. This substitution can occur because the system does not adequately verify the target location of junctions during the restore operation, creating a window where an unprivileged user can place a crafted file at the expected location before the restore process completes. The vulnerability essentially allows for a race condition scenario where the security boundary is breached through improper file system handling.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of the antivirus software. An attacker who gains unprivileged access to a system can leverage this flaw to restore malicious files to privileged locations such as system directories or protected registry locations. This capability enables the execution of arbitrary code with elevated privileges, potentially allowing for complete system compromise. The vulnerability is particularly concerning because it affects the core security functionality of the antivirus software itself, creating a situation where the security tool becomes a vector for exploitation rather than a protective barrier.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and CWE-367 (Time-of-Check to Time-of-Use) categories, demonstrating how inadequate file system validation can create serious security weaknesses. The ATT&CK framework categorizes this issue under privilege escalation techniques, specifically targeting the T1068 (Local Port Forwarding) and T1548.002 (Abuse Elevation Control Mechanism) tactics. The vulnerability also reflects poor input validation practices and inadequate sandboxing of security-critical operations, which are common themes in modern exploit development. Organizations running affected versions of Bitdefender Antivirus Free face significant risk, as this flaw could be exploited by attackers to establish persistent access, escalate privileges, and bypass other security controls that depend on the antivirus software's integrity.
Mitigation strategies should focus on immediate patching of affected systems to version 1.0.17 or later, where the junction handling has been properly addressed. System administrators should also implement monitoring for suspicious file system activities, particularly around quarantine and restore operations. Additionally, organizations should consider implementing least privilege principles and ensuring that antivirus software runs with minimal required privileges to limit the impact of such vulnerabilities. The fix typically involves strengthening the validation of junction points during file operations and implementing proper access controls that prevent unauthorized substitution of quarantined files.