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high advisory

CVE-2026-34344 — Windows Ancillary Function Driver for WinSock Type Confusion Vulnerability

CVE-2026-34344 is a type confusion vulnerability in the Windows Ancillary Function Driver for WinSock, allowing an authorized local attacker to elevate privileges.

CVE-2026-34344 is a type confusion vulnerability affecting the Windows Ancillary Function Driver for WinSock. This vulnerability allows an authorized, local attacker to elevate their privileges on the system. The vulnerability arises from the driver’s handling of resources with incompatible types, leading to a potential privilege escalation. Microsoft has acknowledged the vulnerability and assigned it a CVSS v3.1 score of 7.8, indicating a high severity. Exploitation of this vulnerability requires an attacker to have existing access to the local system.

Attack Chain

  1. The attacker gains initial access to the system with limited privileges.
  2. The attacker crafts a malicious request targeting the Windows Ancillary Function Driver for WinSock.
  3. The request exploits the type confusion vulnerability (CVE-2026-34344) when the driver attempts to access a resource using an incompatible type.
  4. This type confusion allows the attacker to overwrite critical memory locations within the driver’s address space.
  5. The attacker leverages the memory corruption to inject malicious code into the driver’s process.
  6. The injected code executes with the elevated privileges of the Windows Ancillary Function Driver.
  7. The attacker uses the elevated privileges to perform unauthorized actions on the system, such as installing software or modifying system settings.

Impact

Successful exploitation of CVE-2026-34344 allows an attacker to elevate their privileges from a standard user to a higher privileged account, potentially SYSTEM. This could lead to a complete compromise of the affected system, allowing the attacker to install malicious software, modify system data, or create new accounts with administrative rights. The vulnerability affects systems running the Windows Ancillary Function Driver for WinSock.

Recommendation

Detection coverage 2

Detects CVE-2026-34344 Exploitation Attempt — Suspicious AFD.SYS Process Creation

medium

Detects CVE-2026-34344 exploitation attempt — Monitors for process creations where the parent process is afd.sys, which is unusual and could indicate exploitation

sigma tactics: privilege_escalation techniques: T1068 sources: process_creation, windows

Detects CVE-2026-34344 Exploitation Attempt — System Call from AFD.SYS

medium

Detects CVE-2026-34344 exploitation attempt — Monitors for system calls originating from afd.sys, which could indicate malicious code execution after memory corruption

sigma tactics: privilege_escalation techniques: T1068 sources: image_load, windows

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