Description

Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.0",
  "pubDate": "2026-08-11T17:19:08.100Z",
  "pubdate": "2026-08-11T17:19:08.100Z",
  "executiveSummary": "This security analysis evaluates a use-after-free vulnerability affecting the Windows Ancillary Function Driver for WinSock. The flaw resides in kernel-mode memory management where improper object lifetime handling allows an attacker to manipulate dangling pointers.\nThe primary impact of this vulnerability is local elevation of privileges, enabling an authenticated low-privileged user to execute arbitrary code with kernel-level permissions. This compromises the entire operating system security boundary.\nThe affected product is the Windows Ancillary Function Driver for WinSock, a core networking component integral to the Windows kernel architecture. The risk implication is severe, as successful exploitation results in complete system compromise.\nAttacker capabilities require local access to the target system. The attacker must possess authorization to execute code locally, typically through a standard user account or compromised session, to interact with the vulnerable driver interface.\nExploitation requirements include the ability to execute native code on the target host and interact with WinSock driver input/output control operations to trigger the memory corruption sequence.",
  "technicalDetails": "The vulnerability is classified as a use-after-free memory corruption flaw located within the Windows Ancillary Function Driver for WinSock, specifically operating within the kernel space.\nThe root cause stems from inadequate synchronization and reference counting during object teardown or state transitions. When certain driver-managed objects are closed or dereferenced, the underlying memory is freed, but pointers referencing these objects are not appropriately nullified or managed.\nAn authenticated local attacker can exploit this condition by sending carefully crafted input/output control requests to the driver. By manipulating the timing of object allocation and deallocation, the attacker forces the system to reallocate the freed memory region with attacker-controlled data.\nThe attack flow proceeds as follows: First, the attacker initializes communication with the Ancillary Function Driver via standard device handles. Second, the attacker triggers an operation that causes a specific kernel object to be freed while retaining a dangling pointer reference. Third, the attacker performs heap feng-shui to place controlled payloads into the newly vacated memory slot. Finally, referencing the dangling pointer executes the attacker-supplied data as instructions or function pointers.\nThe vulnerable component is the Ancillary Function Driver kernel module responsible for handling low-level socket operations and auxiliary network functions. Affected versions encompass vulnerable builds of the Microsoft Windows operating system utilizing the affected driver implementation.\nAuthentication requirements necessitate local interactive access or the ability to execute code within a standard user session. Network exposure is non-existent, as the vulnerability cannot be triggered remotely without prior local code execution.\nPrivilege requirements are minimal prior to exploitation, as an authenticated user with standard privileges can interface directly with the device driver. Post-exploitation impact results in local elevation of privileges, granting the attacker NT AUTHORITY\\SYSTEM or kernel-level execution capabilities, bypassing all standard security controls."
}