CVE-2026-62799 in Windows
Summary
by MITRE • 08/11/2026
Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical heap-based buffer overflow flaw within the Windows Server Message Block client implementation that enables authenticated attackers to achieve local privilege escalation. The vulnerability stems from inadequate input validation and memory management practices in the smbclient component when processing maliciously crafted network requests or file operations. Attackers who possess valid credentials on the target system can exploit this weakness to overwrite adjacent heap memory locations, potentially leading to arbitrary code execution with elevated privileges. The flaw exists in the client-side processing logic where insufficient bounds checking occurs during buffer allocation and data copying operations, creating opportunities for attackers to manipulate heap metadata and control program execution flow.
The technical exploitation of this vulnerability follows established patterns consistent with heap overflow attacks as documented in the common weakness enumeration framework under CWE-121. The attack vector requires an authenticated user context and leverages the inherent trust relationships within the SMB protocol implementation. When legitimate SMB client operations process malformed data structures, the heap management functions fail to properly validate buffer boundaries, allowing attackers to overwrite critical memory regions including function pointers, return addresses, or other control data structures. This vulnerability aligns with attack techniques categorized under the attack pattern taxonomy as described in the MITRE ATT&CK framework where privilege escalation occurs through local exploit development.
The operational impact of this vulnerability extends beyond simple privilege elevation to potentially enable full system compromise when combined with other attack vectors or when executed within environments containing additional security weaknesses. The affected Windows SMB client component operates with elevated privileges during normal operation, making successful exploitation particularly dangerous as it can allow attackers to bypass standard user access controls and gain administrative rights. Organizations running Windows systems that utilize SMB file sharing services face significant risk exposure, especially in environments where authentication credentials might be compromised through social engineering or credential theft attacks.
Mitigation strategies should prioritize immediate patch deployment from Microsoft security updates which address the underlying heap management issues through proper buffer boundary validation and memory allocation practices. Network segmentation and access control measures can help limit potential exploitation by restricting unauthorized authentication attempts to vulnerable systems. Additional defensive controls include implementing strict SMB protocol version restrictions, disabling unnecessary SMB services where possible, and monitoring for anomalous SMB client behavior that might indicate exploitation attempts. Security teams should also consider deploying application whitelisting solutions to prevent execution of malicious payloads from untrusted sources while maintaining comprehensive logging and alerting mechanisms to detect potential exploitation activities. Regular vulnerability assessments and penetration testing can help identify systems that may still be exposed through misconfigurations or delayed patch management processes.