Cve-2025-32709: Privilege Escalation Via Afd.Sys Actively Exploited In Targeted Attacks

A zero-day vulnerability in the Windows Ancillary Function Driver for WinSock (AFD) is being actively exploited in the wild. The flaw allows attackers with basic user privileges to gain administrative control over target systems, enabling deployment of credential harvesters and ransomware payloads in targeted campaigns.

Severity Level: High

VULNERABILITY OVERVIEW:

1. Vulnerability Details:
   • CVE: CVE-2025-32709
   • CVSS score: 7.8
   • Description: Use After Free (CWE-416) issue in the Windows Ancillary Function Driver for WinSock that allows an authorized malicious user to elevate privileges locally.
   • Affected sector is healthcare and government sectors since April 2025.
   • The vulnerability is actively exploited in the wild
   • Affects: Windows 10, Windows 11 and Windows Server 2008, 2012, 2016, 2019, 2025, 2022, 2025
2. Initial Access Likely Via:
   • Phishing Emails with malicious attachments or links that deliver first-stage malware loaders.
   • Compromised Credentials obtained through brute-force attacks or infostealers.
   • Exposed Remote Desktop Protocol (RDP) Endpoints and Terminal Servers, especially in poorly segmented network environments.
3. Exploitation:
   • AFD.sys (Ancillary Function Driver for WinSock) is a kernel-mode driver responsible for socket operations.
   • The vulnerability is triggered via crafted IOCTL calls or malformed Winsock interactions, which manipulate driver memory.
   • The exploit abuses legitimate API pathways, leaving minimal or no forensic traces, bypassing traditional signature-based detections.
   • This zero-day allows silent elevation of privilege, which results in deploying rootkits, disabling defences, or manipulating services.
4. Post-exploitation: credential dumping or ransomware deployment

Recommendations:

1. Ensure that the affected Windows Workstations and Servers are updated with the latest security patches.
2. Enable HVCI (Hypervisor-Protected Code Integrity) to prevent kernel-level exploitation on supported Windows devices.
3. Restrict local and domain administrator privileges to only essential personnel to limit the impact of privilege escalation exploits.
4. Monitor for anomalous AFD.sys memory allocation patterns using Defender for Endpoint.

Source:

• https://gbhackers.com/windows-ancillary-for-winsock-0-day-vulnerability-exploited/
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-32709

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