CVE-2026-83738 in Windows
Summary
by MITRE • 10/14/2026
Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a use-after-free condition within the Windows Ancillary Function Driver for WinSock, commonly referred to as AFD.sys. This driver is a critical component of the Microsoft TCP/IP stack implementation on Windows operating systems, responsible for managing socket-related operations and facilitating communication between user-mode applications and kernel-mode network drivers. The specific flaw arises from improper memory management practices within this driver, where a pointer to a previously freed memory block remains accessible or is referenced after its deallocation has occurred. This type of error creates an opportunity for local privilege escalation when exploited by an attacker who already possesses valid authentication credentials on the affected system.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to manipulate kernel memory structures in ways that can bypass standard security controls. In this context, if an authorized user triggers the specific sequence of operations that leads to the premature freeing of a memory object while other references to that object still exist within the driver's internal state, the attacker may be able to control what data is written into that freed memory region through heap spraying or similar techniques. By carefully crafting malicious input, it becomes possible to overwrite critical kernel pointers or function addresses with controlled values. When the system subsequently attempts to use these corrupted references, execution flow can be redirected to arbitrary code running in kernel mode, effectively granting the attacker full control over the operating system's core functions.
The operational impact of this vulnerability is severe due to its potential for local privilege escalation. An authenticated user on a compromised workstation or server could leverage this flaw to execute arbitrary code with SYSTEM-level privileges. This transformation from standard user rights to administrative kernel access allows the attacker to install persistent backdoors, dump sensitive credentials stored in memory, modify security policies, and disable defensive mechanisms such as antivirus software or endpoint detection systems. Because AFD.sys is integral to network connectivity on Windows platforms, this vulnerability affects a wide range of Microsoft operating systems that include this component, making it a high-value target for threat actors seeking deep access within enterprise environments without requiring external exploitation vectors like remote code execution.
In terms of industry classification standards, this flaw aligns with CWE-416, which defines use-after-free errors as situations where software continues to use memory after it has been freed, leading to undefined behavior and potential security breaches. Furthermore, the exploitation technique maps directly to MITRE ATT&CK tactic T1068, specifically sub-technique T1068.002 for Exploitation for Privilege Escalation. This categorization highlights how attackers transition from lower-level access to higher-level privileges by exploiting weaknesses in system components that handle sensitive operations like network socket management. Understanding these mappings helps security teams prioritize patching efforts and configure detection rules based on known exploitation patterns associated with kernel memory corruption vulnerabilities.
Mitigation strategies primarily rely on the timely application of vendor-provided security updates released by Microsoft to address this specific flaw within AFD.sys. Organizations should ensure that all endpoints are patched according to their standard vulnerability management lifecycle, prioritizing systems exposed to untrusted users or those hosting services accessible via network interfaces where local account compromise is a risk vector. Additionally, implementing strict application whitelisting and restricting user privileges can reduce the attack surface by limiting which accounts have access to trigger potentially vulnerable code paths within kernel drivers. Security monitoring solutions should also be configured to detect anomalous behavior indicative of memory corruption attempts or unexpected privilege changes originating from system processes associated with network stack operations.