CVE-2026-62784 in Windows
Summary
by MITRE • 08/11/2026
Heap-based buffer overflow in Microsoft Local Security Authority Server (lsasrv) allows an authorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 08/11/2026
This heap-based buffer overflow vulnerability exists within the Microsoft Local Security Authority Server component known as lsasrv which forms a critical part of the Windows authentication infrastructure. The flaw manifests when the lsasrv service processes certain input data structures that are improperly validated before being copied into fixed-size memory buffers allocated on the heap. This specific vulnerability falls under the Common Weakness Enumeration category CWE-121 Heap-based Buffer Overflow, where insufficient bounds checking allows attackers to overwrite adjacent heap memory regions. The vulnerability is particularly concerning because it operates within a privileged system component that handles authentication requests from remote clients and local processes.
The technical execution of this vulnerability requires an authorized attacker who has already established some level of access to the target system or network, as the attack vector involves sending specially crafted authentication requests to the lsasrv service. When the service receives malformed input data that exceeds the allocated buffer size, it fails to properly validate the input length before copying the data into memory, resulting in a heap corruption condition. This heap corruption can then be exploited to overwrite critical function pointers, return addresses, or other control data structures within the heap memory layout, potentially allowing an attacker to redirect execution flow and execute arbitrary code with the privileges of the lsasrv service, which typically runs with SYSTEM level privileges.
The operational impact of this vulnerability extends beyond simple remote code execution as it provides attackers with a powerful foothold within Windows environments. Since lsasrv is responsible for processing authentication requests including Kerberos tickets and NTLM authentication exchanges, exploitation could enable attackers to impersonate legitimate users or gain access to sensitive domain resources. The vulnerability's network-based nature means that attackers do not require physical access to the target system, making it particularly dangerous in enterprise environments where Windows domain controllers are frequently exposed to external networks. This particular weakness aligns with attack techniques described in the MITRE ATT&CK framework under T1078 Valid Accounts and T1566 Phishing, as exploitation typically requires initial access through other means followed by privilege escalation through this authentication service vulnerability.
Mitigation strategies for this heap-based buffer overflow should include immediate deployment of Microsoft security updates that address the specific vulnerability in lsasrv, along with network segmentation to limit access to domain controller services. Additional protective measures include implementing network access controls to restrict communication between domain controllers and untrusted networks, enabling advanced threat protection features such as Windows Defender Application Control, and monitoring for unusual authentication patterns that might indicate exploitation attempts. Organizations should also consider reducing the attack surface by disabling unnecessary authentication protocols and ensuring that only essential services are exposed to external network traffic, while maintaining comprehensive logging of authentication events to detect potential exploitation activities through behavioral analysis techniques.