CVE-2026-88149 in Windows
Summary
by MITRE • 10/14/2026
Double 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 as a double free condition within the Windows Ancillary Function Driver for WinSock represents a critical memory management flaw that can be exploited by authenticated users to achieve local privilege escalation. This driver, known in system internals as afwpkt.sys or similar variants depending on the specific update cycle, serves as an intermediary layer between user-mode applications and kernel-mode network stack components. It facilitates advanced packet filtering and processing capabilities required for modern networking features such as Windows Filtering Platform integration. The core technical flaw resides in how the driver handles memory deallocation during complex state transitions or error handling routines within its IOCTL (Input/Output Control) handlers. Specifically, when a crafted sequence of requests is sent to the driver via standard WinSock APIs, the internal logic fails to properly track reference counts or pointer validity before attempting to release allocated kernel pool memory more than once for the same object instance.
In Windows operating systems, kernel-mode drivers operate with high privileges and direct access to physical memory structures. A double free vulnerability allows an attacker to corrupt the non-paged pool metadata used by the Memory Manager. By triggering this flaw repeatedly or in conjunction with specific timing conditions, a local user can manipulate the heap allocator's internal data structures. This corruption enables arbitrary read/write primitives within kernel space, which are essential for bypassing security mechanisms such as Kernel Patch Protection (PatchGuard) and User Mode Execution Prevention (UMEP). The exploitation path typically involves crafting malicious socket options or packet filter rules that trigger the erroneous deallocation sequence while simultaneously allocating controlled memory at the same address to overwrite critical function pointers or object headers.
The operational impact of this vulnerability is severe, as it directly compromises the integrity of the operating system's core security boundary. An attacker who successfully exploits this flaw can execute arbitrary code with SYSTEM-level privileges, effectively gaining full control over the compromised host. This level of access allows for the installation of rootkits, persistence mechanisms, credential theft from memory dumps, and lateral movement within a network environment. Because the vulnerability exists in a component that handles standard networking operations, it may be triggered by applications that perform legitimate but complex socket configurations, making detection through behavioral analysis challenging without deep packet inspection or strict application whitelisting. The presence of this flaw undermines trust in the local security authority and can lead to complete system compromise if left unpatched.
Mitigation strategies primarily rely on applying the latest cumulative updates provided by Microsoft, which include patches that correct the memory management logic within the affected driver components. Administrators should ensure that all systems are updated with the most recent security rollups specifically targeting kernel-mode vulnerabilities in network drivers. In environments where immediate patching is not feasible, restricting access to WinSock IOCTL interfaces through strict application control policies can reduce the attack surface. Additionally, enabling advanced auditing for process creation and driver loading events may help detect exploitation attempts by monitoring for unusual patterns of memory allocation or privilege changes originating from non-system processes interacting with network drivers. Regular vulnerability scanning focused on kernel-level components is also recommended to identify unpatched instances before they can be leveraged in targeted attacks.
This type of flaw aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-415, which describes Double Free vulnerabilities resulting from improper handling of memory deallocation operations. Furthermore, the exploitation technique maps to MITRE ATT&CK tactics related to Privilege Escalation and Defense Evasion, specifically techniques involving kernel exploit development and driver manipulation. Understanding these mappings helps security teams prioritize remediation efforts based on established industry frameworks for risk assessment and vulnerability management. The persistence of such vulnerabilities in core system components underscores the importance of rigorous code review processes and fuzzing methodologies during the development lifecycle of critical infrastructure drivers to prevent similar memory corruption issues from reaching production environments.