CVE-2026-49801 in Windows
Summary
by MITRE • 07/14/2026
Use of uninitialized resource in Windows SMB allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical information disclosure flaw within the Windows Server Message Block protocol implementation that affects authenticated users with local access privileges. The issue stems from improper initialization of system resources during SMB processing operations, creating potential pathways for unauthorized data exposure. According to CWE-457, this manifests as the use of uninitialized memory locations that may contain residual data from previous operations, potentially exposing sensitive information including credentials, session tokens, or system configuration details. The vulnerability operates within the Windows kernel networking stack where SMB services process incoming requests and maintain state information for connected clients.
The technical exploitation occurs when an authenticated local user leverages specific SMB protocol interactions to trigger memory access patterns that reveal uninitialized resource contents. This typically involves crafting malicious SMB requests or exploiting existing SMB service functionality that fails to properly initialize memory buffers before processing user-supplied data. The flaw exists in the Windows SMB server implementation where certain resource allocation routines do not adequately clear memory regions, leaving residual data accessible through subsequent operations. Attackers can potentially harvest sensitive information such as cryptographic keys, authentication tokens, or system configuration parameters that were previously stored in the uninitialized memory locations.
From an operational perspective, this vulnerability creates significant security implications for Windows environments where local user access is granted to systems running SMB services. The attack requires only local authentication privileges and does not necessitate network-level access or specialized exploitation techniques. However, the impact extends beyond simple information disclosure as the leaked data could potentially enable further attacks including privilege escalation, credential harvesting, or system compromise. Organizations with multiple users having local access to SMB-enabled systems face heightened risk since any authenticated user can potentially exploit this weakness to gain unauthorized visibility into system resources.
The vulnerability aligns with ATT&CK technique T1087.001 for account discovery and T1552.001 for credentials in files, as leaked memory contents may contain sensitive authentication information or system configuration details that could be leveraged by attackers. Mitigation strategies include applying Microsoft security updates that properly initialize SMB resource handling routines and implementing network segmentation to limit local access privileges where possible. Additionally, organizations should consider reducing local user privileges on systems running SMB services and monitoring for anomalous SMB protocol behavior that might indicate exploitation attempts. The fix typically involves proper memory initialization before resource allocation within the SMB server implementation to prevent residual data exposure during subsequent processing operations.