CVE-2020-1535 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists when the Windows Backup Engine improperly handles memory. To exploit this vulnerability, an attacker would first have to gain execution on the victim system. An attacker could then run a specially crafted application to elevate privileges. The security update addresses the vulnerability by correcting how the Windows Backup Engine handles memory.
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability described in CVE-2020-1535 represents a critical elevation of privilege flaw within the Windows Backup Engine component, classified under CWE-125 as an out-of-bounds read condition that can lead to privilege escalation. This vulnerability stems from improper memory handling mechanisms within the backup engine's execution flow, specifically when processing backup operations that involve memory allocation and deallocation sequences. The flaw allows an attacker to manipulate memory structures in a way that bypasses normal access controls and privilege boundaries. The vulnerability is particularly concerning because it requires only initial execution access on the target system to be exploited, making it a prime target for attackers who have already achieved a foothold through other means such as phishing attacks or exploit kits. According to the ATT&CK framework, this vulnerability maps to T1068 (Local Privilege Escalation) and T1547 (Registry Run Keys/Startup Folder) as attackers can leverage the elevated privileges to establish persistence mechanisms.
The technical implementation of this vulnerability occurs when the Windows Backup Engine processes backup operations that involve complex memory management scenarios. During backup execution, the engine allocates memory blocks for temporary data storage, file processing, and metadata handling. The improper handling manifests when the engine fails to properly validate memory boundaries during these operations, potentially allowing an attacker to overwrite memory locations or manipulate pointers that control access to system resources. The vulnerability specifically impacts systems running Windows 10 versions 1903 and 1909, as well as Windows Server 2019 and Windows Server 2016, where the backup engine components are most susceptible to memory corruption attacks. Attackers can exploit this by crafting malicious applications that trigger specific memory access patterns during backup operations, leading to privilege escalation from standard user to system level access.
The operational impact of CVE-2020-1535 extends beyond simple privilege escalation, as it provides attackers with the capability to execute arbitrary code with elevated privileges and potentially access sensitive system resources. Once successfully exploited, an attacker gains access to the full system namespace, including the ability to read and modify protected registry entries, access encrypted data, and manipulate system files that would normally be restricted to administrators. The vulnerability's exploitation requires minimal privileges to begin with, making it particularly dangerous in environments where users have standard accounts but can still execute applications through legitimate business processes. Organizations with backup automation systems or scheduled backup tasks are especially at risk, as these systems often run with elevated privileges and may be targeted by attackers seeking persistent access. The vulnerability can also be leveraged to establish persistence mechanisms by modifying backup configurations or creating malicious backup scripts that maintain access across system reboots.
Microsoft's security update for CVE-2020-1535 addresses the root cause by implementing proper memory boundary checks and validation within the Windows Backup Engine's memory management routines. The patch corrects how the backup engine handles memory allocation, deallocation, and access patterns during backup operations, ensuring that memory operations remain within valid boundaries and that proper access controls are enforced. Organizations should prioritize deployment of this update across all affected Windows systems, particularly those running Windows 10 versions 1903 and 1909, as well as Windows Server 2016 and 2019. Additional mitigations include implementing application whitelisting policies to prevent execution of unauthorized applications, disabling unnecessary backup services, and monitoring for suspicious backup operations that may indicate exploitation attempts. Network segmentation and least privilege access controls should be implemented to limit the potential impact of successful exploitation, while regular security assessments should be conducted to identify systems that may still be vulnerable to related attack vectors. The vulnerability underscores the importance of proper memory management practices in system components and the critical need for regular security updates to address emerging threats in backup and recovery systems.