CVE-2020-1556 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists in the way that the Windows WalletService handles objects in memory. An attacker who successfully exploited the vulnerability could execute code with elevated permissions. To exploit the vulnerability, a locally authenticated attacker could run a specially crafted application. The security update addresses the vulnerability by ensuring the Windows WalletService properly handles objects in memory.
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability identified as CVE-2020-1556 represents a critical elevation of privilege flaw within the Windows WalletService component that operates as part of Microsoft's Windows operating system ecosystem. This weakness specifically manifests in the service's improper handling of memory objects, creating a pathway for malicious actors to escalate their privileges from standard user level to system-level execution. The vulnerability resides within the Windows WalletService which manages digital wallet credentials and sensitive authentication data, making it a particularly attractive target for attackers seeking persistent system access. The flaw is categorized under CWE-121, which describes heap-based buffer overflow conditions, though the specific implementation involves improper memory management rather than traditional buffer overflows. The attack vector requires local authentication, meaning an adversary must first establish a valid user session before attempting exploitation, but this prerequisite does not significantly limit the threat surface given the prevalence of local access points in enterprise environments.
The technical exploitation of this vulnerability occurs through the manipulation of memory objects that the Windows WalletService processes during normal operation. When the service handles certain credential data structures in memory, it fails to properly validate or sanitize the input objects, potentially allowing an attacker to craft malicious payloads that trigger unauthorized code execution. This memory handling flaw enables attackers to execute arbitrary code with the elevated privileges of the WalletService process, which typically operates with system-level permissions due to its role in managing sensitive authentication credentials. The exploitation process involves running a specially crafted application that leverages the service's memory handling weakness to inject and execute malicious code within the privileged context. This mechanism aligns with ATT&CK technique T1068, which covers the use of local privilege escalation through service manipulation and memory corruption vulnerabilities. The attack's success demonstrates the dangerous intersection of improper input validation and privilege escalation opportunities within Windows system services.
The operational impact of CVE-2020-1556 extends beyond simple privilege escalation, as it provides attackers with a persistent foothold within Windows environments where the WalletService operates. Once exploited, the vulnerability enables attackers to maintain elevated access while potentially accessing other system resources that require higher privileges, including credential storage areas, network configurations, and system-level processes. The vulnerability affects multiple Windows versions including Windows 10 and Windows Server 2019, making it particularly concerning for enterprise environments where these systems are prevalent. Organizations running affected systems face significant risk of data compromise, lateral movement attacks, and potential complete system takeover. The vulnerability's impact is amplified by the fact that the WalletService typically runs with elevated privileges, meaning successful exploitation provides attackers with immediate access to sensitive system functions and data that would otherwise be protected by standard user access controls. This makes the vulnerability particularly dangerous in environments where multiple users share systems or where the service runs continuously in the background.
Microsoft addressed this vulnerability through a comprehensive security update that focuses on improving the memory handling procedures within the Windows WalletService. The patch ensures proper validation and sanitization of memory objects before processing, eliminating the conditions that allowed attackers to exploit the privilege escalation opportunity. Organizations should prioritize deployment of this update across all affected Windows systems, particularly those running Windows 10 and Windows Server 2019 versions that were vulnerable to the flaw. The mitigation strategy should include comprehensive vulnerability scanning to identify systems running affected versions of the WalletService, followed by immediate patch deployment and monitoring for any signs of exploitation attempts. Security teams should also implement additional controls such as monitoring for unusual WalletService activity, restricting local user access where possible, and maintaining detailed audit logs of service operations. Given the nature of the vulnerability, regular security assessments of Windows service components and memory handling practices should be part of ongoing security monitoring programs to prevent similar issues from emerging in other system components.