Description

Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:34.180Z",
  "pubdate": "2026-08-11T17:18:34.180Z",
  "executiveSummary": "This vulnerability is classified as a heap-based buffer overflow affecting the Windows SMB Client. The primary security impact of this flaw is local privilege escalation, enabling an attacker to execute arbitrary code with elevated permissions on the underlying operating system.\nThe affected product is the Windows SMB Client. The risk implications are severe, as successful exploitation allows a local user to bypass security boundaries and gain administrative or system-level access, potentially leading to full compromise of the host.\nAttacker capabilities require local access to the target system. The attacker must already be authorized or possess the ability to execute code locally to interact with the vulnerable Windows SMB Client component.\nExploitation requirements include local execution context and the ability to interact with the SMB client subsystem to trigger the heap memory corruption condition. No specific network exposure is inherently required since the vulnerability manifests locally, though the SMB protocol handling logic is central to the flaw.",
  "technicalDetails": "The vulnerability resides within the Windows SMB Client component, specifically related to how memory allocations and buffer management are handled during the processing of Server Message Block protocol operations.\nThe root cause is a heap-based buffer overflow, occurring when the vulnerable component fails to properly validate the size boundaries of incoming data before writing it to a heap-allocated memory buffer. Insufficient bounds checking leads to a heap corruption condition when data exceeding the allocated buffer capacity is processed.\nThe affected versions include the standard Windows SMB Client implementations as specified by the vulnerable system context. The vulnerability requires local access, and the attacker must be an authorized user on the local system to initiate the sequence of operations that interact with the vulnerable SMB client functions.\nThe attack flow begins with the local attacker preparing a malicious payload or interacting with the local SMB client subsystem in a manner that forces the processing of oversized or malformed data structures. Step-by-step, the exploitation occurs as follows: first, the attacker establishes local execution and targets the SMB client interface or API; second, the attacker supplies specially crafted input designed to exceed the expected bounds of the destination heap buffer; third, the vulnerable function performs a memory write operation without adequate length verification, resulting in a heap-based buffer overflow; fourth, the overflow corrupts adjacent heap metadata or critical function pointers residing in the heap space.\nPayload behavior following the heap corruption typically involves hijacking execution flow by overwriting function pointers or manipulating heap structures to achieve arbitrary code execution. The post-exploitation impact allows the attacker to elevate privileges locally, transitioning from a standard user context to a privileged security context such as SYSTEM or Administrator, thereby subverting the host operating system access controls."
}