CVE-2025-49762 in Windows
Summary
by MITRE • 08/12/2025
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 11/21/2025
The vulnerability identified as CVE-2025-49762 represents a critical race condition flaw within the Windows Ancillary Function Driver for WinSock component, specifically affecting the ws2ifsl.sys driver. This race condition manifests when multiple threads or processes attempt concurrent access to shared resources without proper synchronization mechanisms, creating a window of opportunity for malicious exploitation. The flaw exists in the kernel-level driver responsible for managing network interface functionality, making it particularly dangerous as it operates with elevated privileges and can be leveraged by authorized local users to achieve privilege escalation. The vulnerability is categorized under CWE-362, which specifically addresses race conditions in software systems, and aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel exploits. The affected driver component is integral to Windows networking operations and handles various socket-related functions including interface enumeration, configuration management, and network protocol handling.
The technical implementation of this race condition occurs when the ws2ifsl.sys driver processes concurrent requests to shared kernel memory structures or data objects without appropriate locking mechanisms. An authorized local attacker can exploit this weakness by carefully timing multiple simultaneous operations against the vulnerable driver interface, creating a scenario where the driver's internal state becomes inconsistent or corrupted. This improper synchronization allows the attacker to manipulate shared resources in ways that were not intended by the original design, potentially leading to arbitrary code execution in kernel space. The vulnerability is particularly concerning because it requires no special privileges beyond local user access, yet can be leveraged to gain SYSTEM-level privileges through the driver's elevated execution context. The race condition typically involves scenarios where the driver performs operations on shared data structures such as network interface configurations, socket state information, or internal buffer management without proper mutual exclusion controls.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a reliable method to bypass standard Windows security controls and gain unauthorized administrative access to affected systems. The attack surface is significant since the ws2ifsl.sys driver is actively used across various Windows versions and network configurations, making the vulnerability widespread and difficult to mitigate completely. Once exploited, the attacker can execute malicious code with kernel-level privileges, potentially leading to complete system compromise, data exfiltration, or establishment of persistent backdoors. The vulnerability's exploitation requires local access and can be performed without network connectivity, making it particularly stealthy and difficult to detect through network-based monitoring systems. The attack vector is especially dangerous in enterprise environments where local user accounts may have legitimate access to systems but could be compromised through social engineering or credential theft, providing attackers with the necessary local access to exploit this vulnerability.
Mitigation strategies for CVE-2025-49762 should include immediate deployment of Microsoft security updates and patches that address the race condition in the ws2ifsl.sys driver. Organizations should implement comprehensive monitoring of kernel-level activity and unusual privilege escalation attempts, particularly focusing on processes that interact with network interface management components. The principle of least privilege should be enforced by limiting local user accounts to only necessary permissions and implementing strict access controls for network interface management operations. Additionally, system administrators should conduct regular security assessments of kernel drivers and network components to identify potential synchronization issues. Network segmentation and endpoint detection and response solutions can help detect anomalous behavior indicative of exploitation attempts. The vulnerability demonstrates the critical importance of proper synchronization mechanisms in kernel-level drivers and serves as a reminder that even authorized local users can pose significant threats when operating in environments with poorly designed concurrency controls. Security teams should also consider implementing application whitelisting policies to restrict execution of unauthorized code and maintain regular vulnerability assessments to identify similar race condition vulnerabilities in other system components.