CVE-2021-1640 in Windows
Summary
by MITRE • 03/11/2021
Windows Print Spooler Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-26878.
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Analysis
by VulDB Data Team • 03/30/2021
The Windows Print Spooler Elevation of Privilege Vulnerability identified as CVE-2021-1640 represents a critical security flaw within Microsoft's print subsystem that allows local attackers to escalate their privileges from standard user level to system level. This vulnerability specifically affects the Windows Print Spooler service which manages print jobs and printer communications across Windows operating systems. The flaw resides in how the print spooler service handles certain print job submissions and file operations, creating an opportunity for malicious code execution with elevated privileges. This vulnerability is particularly concerning because it enables attackers to gain system-level access without requiring remote exploitation capabilities, making it a significant threat vector for local privilege escalation attacks.
The technical implementation of this vulnerability stems from improper input validation and privilege handling within the print spooler component. When processing print jobs, the service fails to properly validate certain parameters and file operations, allowing maliciously crafted print job submissions to execute code with system-level privileges. The vulnerability manifests when the spooler service processes specific print job data structures that contain malicious payloads or manipulated file paths. This flaw is categorized under CWE-264, which represents permissions, privileges, and access control issues, specifically focusing on inadequate privilege management during file operations. The vulnerability affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, with the most severe impact occurring on systems running with default security configurations.
The operational impact of CVE-2021-1640 extends beyond simple privilege escalation, as it provides attackers with complete system control capabilities once exploited. An attacker with local access can leverage this vulnerability to install backdoors, modify system files, access sensitive data, and establish persistent access to the compromised system. The vulnerability's exploitation requires minimal prerequisites since it only requires local user access, making it particularly dangerous in environments where user accounts have broad access rights. Attackers can combine this vulnerability with other techniques to create more sophisticated attack chains, potentially leading to network-wide compromise. The vulnerability's presence in the print spooler service also means that any application or user that can submit print jobs can potentially exploit this flaw, creating a wide attack surface that extends beyond traditional security boundaries.
Mitigation strategies for CVE-2021-1640 should focus on both immediate remediation and long-term security hardening measures. Microsoft has released security updates that address this vulnerability through patches to the Windows Print Spooler service, which should be deployed immediately across all affected systems. Organizations should also implement additional security controls such as disabling the print spooler service when not actively needed, implementing least privilege access controls for print job submissions, and monitoring print spooler activity for suspicious patterns. Network segmentation and access controls should be reinforced to limit local user access to critical system components. The vulnerability aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and T1547.009 which addresses "Print Processors" as a method of persistence and privilege escalation. Security teams should also consider implementing behavioral monitoring solutions that can detect anomalous print spooler activity patterns that may indicate exploitation attempts. Regular vulnerability assessments and penetration testing should include evaluation of print spooler configurations to ensure proper security hardening measures are in place.