Description

Heap-based buffer overflow in Windows SMB Server allows an authorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-08-11T17:18:32.770Z",
  "pubdate": "2026-08-11T17:18:32.770Z",
  "executiveSummary": "This vulnerability is a heap-based buffer overflow affecting the Windows Server Message Block (SMB) Server implementation. The flaw enables an authorized network attacker to achieve remote code execution on vulnerable systems. The primary impact of successful exploitation includes complete system compromise, unauthorized execution of arbitrary code with elevated privileges, and potential lateral movement across the network domain. Affected systems encompass standard deployments of Windows SMB Server that process network requests inadequately. The risk implications are severe due to the core network-facing nature of the service and the capability for wormable propagation if combined with other vulnerabilities. Attacker capabilities require network access to the SMB service and valid authorization, implying that the adversary must either possess internal credentials or leverage a separate authentication bypass. Exploitation requirements mandate that the target SMB Server processes maliciously crafted requests that exceed allocated heap memory bounds during memory management operations.",
  "technicalDetails": "The root cause of the vulnerability stems from improper bounds checking within the heap memory allocation and management routines of the Windows SMB Server component when handling specific protocol requests. The vulnerable component is the kernel-mode driver responsible for parsing and managing SMB protocol communications over the network. Network exposure is direct, as the SMB service typically listens on TCP ports 445 and 139, exposing the parsing logic to remote inputs from connected clients. Authentication requirements dictate that the attacker must be authorized, meaning the exploitation vector requires established session credentials or authenticated access to the SMB service. Privilege requirements for initiating the attack are limited to standard network access with basic authorization, but successful code execution typically yields high-privilege kernel-level execution contexts. The exploitation method relies on supplying an oversized or maliciously formatted input payload during a memory allocation sequence within the heap. As the SMB Server processes the incoming request, it calculates insufficient buffer sizes or fails to validate the length parameters supplied in the packet headers. Consequently, when the data is copied into the heap-based buffer, a heap overflow occurs, corrupting adjacent heap metadata and control structures. The attack flow proceeds as follows: first, the authenticated attacker establishes a network connection to the target SMB Server. Second, the attacker transmits a specially crafted SMB packet designed to trigger the vulnerable memory allocation routine. Third, the oversized payload overflows the designated heap buffer, overwriting critical internal structures or function pointers residing in the heap. Finally, when the application or kernel invokes the corrupted pointer, execution flow is redirected to the attacker-supplied shellcode or payload. Payload behavior at this stage involves executing arbitrary instructions within the context of the vulnerable kernel or system service, leading to full system compromise. Post-exploitation impact includes persistent unauthorized access, data exfiltration, deployment of secondary malware, and escalation of privileges across the enterprise network."
}