CVE-2026-105726 in Defender for Endpoint
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Microsoft Defender allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified as an out-of-bounds read within the Microsoft Defender security suite represents a critical memory safety flaw that compromises the integrity of data processing operations performed by the endpoint protection agent. This specific defect occurs when the application attempts to access memory locations beyond the boundaries of allocated buffers, typically due to insufficient validation of input parameters or incorrect calculation of array indices during routine scanning or monitoring activities. Because Microsoft Defender operates with high privileges and deep system integration to monitor file systems, registry keys, and process behaviors, such a flaw can be triggered by local interactions that involve malformed data structures passed to the component responsible for parsing these inputs. The core technical issue lies in the failure of the software to properly verify whether the requested memory address falls within the valid range of the buffer before performing the read operation, leading to the retrieval of unintended data from adjacent memory regions.
From an operational perspective, this vulnerability allows an authorized attacker with local access to disclose sensitive information that resides on the same machine as the compromised system. The impact is primarily focused on confidentiality rather than availability or integrity in its immediate execution phase, although the disclosed information can serve as a stepping stone for further exploitation. By reading memory contents outside of the intended buffer, the attacker may extract cryptographic keys, session tokens, internal state variables, or other sensitive data that was not meant to be accessible through normal application interfaces. This type of disclosure undermines the trust model of the endpoint security solution itself, potentially revealing details about system configuration or user credentials that could facilitate more severe attacks such as privilege escalation or lateral movement within a network environment.
The classification of this flaw aligns with Common Weakness Enumeration (CWE) standards, specifically mapping to CWE-125 Out-of-bounds Read and CWE-787 Out-of-bounds Write depending on the specific memory access pattern observed during exploitation attempts. In terms of tactical behavior within an attack lifecycle, this vulnerability supports techniques associated with ATT&CK ID T1003 Credential Dumping if sensitive credentials are exposed in memory, or T1059 Command and Scripting Interpreter if the disclosed data aids in crafting further commands. It also relates to information gathering phases where attackers seek to understand system internals before executing more destructive payloads. The presence of such a flaw indicates gaps in secure coding practices regarding bounds checking and input validation within the development lifecycle of the security software itself.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided patches that address the underlying memory management errors through rigorous code review and static analysis tools designed to detect buffer over-read conditions. Organizations should ensure that Microsoft Defender is updated to the latest version which includes fixes for known out-of-bounds access issues in its parsing modules. Additionally, implementing strict least-privilege principles can limit the potential impact of local exploitation by restricting user permissions on systems running vulnerable versions of the software. Monitoring system logs for unusual memory access patterns or anomalies reported by other security controls may also provide early detection indicators while patching efforts are underway to restore full confidence in the endpoint protection capabilities.