CVE-2026-70342 in Windows
Summary
by MITRE • 09/09/2026
Use after free in Windows Ancillary Function Driver for WinSock allows an unauthorized attacker to elevate privileges over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as a use-after-free condition within the Windows Ancillary Function Driver for WinSock represents a critical security flaw that compromises the integrity of the operating system's networking stack. This specific driver, often referred to by its file name afwpkt.sys or similar variants depending on the version, serves as an intermediary layer between user-mode applications and kernel-mode network drivers. It facilitates various ancillary functions required for WinSock operations, including packet filtering, QoS management, and other advanced network features. The core technical flaw lies in the improper handling of memory deallocation within this driver's codebase. Specifically, a pointer to a previously allocated memory block is retained after that memory has been freed or released back to the system pool. This creates a dangling pointer scenario where subsequent operations may attempt to access or manipulate data at the address of the now-invalidated memory region.
From an exploitation perspective, this use-after-free vulnerability allows an unauthorized attacker who can execute code within the context of a local user account to trigger the flawed logic sequence. By carefully crafting specific network requests or API calls that interact with the WinSock ancillary functions, an attacker can force the driver to free a memory object while maintaining references to it elsewhere in its internal structures. When these stale references are subsequently dereferenced, they point to arbitrary locations in kernel space. If the attacker can control the content of the freed memory through heap spraying techniques or by allocating new objects at the same address before the dangling pointer is accessed, they can achieve arbitrary code execution with high privileges. This mechanism effectively bypasses standard user-mode restrictions and allows for direct interaction with sensitive kernel structures.
The operational impact of this vulnerability is severe due to its potential for privilege escalation. Since the flaw resides in a component that runs at Kernel Level (CWE-250), successful exploitation grants an attacker full control over the operating system. This means complete read, write, and execute access to all processes running on the machine, including security software such as antivirus programs and firewalls, which can be disabled or manipulated to hide further malicious activity. Furthermore, because this vulnerability is network-related, it may potentially be exploitable remotely if there are entry points that allow unauthenticated users to trigger the specific WinSock ancillary functions involved in the flaw. Even if limited to local exploitation, an attacker with low-level access could escalate their privileges to SYSTEM level, effectively taking full control of the compromised host and using it as a pivot point for lateral movement within the network infrastructure.
Mitigation strategies primarily involve applying vendor-provided security patches that correct the memory management logic within the affected driver version. Organizations should prioritize updating Windows systems to ensure they have the latest cumulative updates which address these kernel-level vulnerabilities. In environments where immediate patching is not feasible, implementing strict application whitelisting and restricting execution of untrusted binaries can reduce the attack surface by preventing unauthorized code from executing in user mode that could trigger the exploit chain. Additionally, network segmentation and monitoring for anomalous WinSock API calls or unusual memory allocation patterns associated with heap spraying techniques can help detect attempted exploitation activities before they result in a successful compromise. Regular vulnerability assessments focusing on kernel drivers and networking components are essential to maintain a robust security posture against such high-severity flaws.