EUVD-2026-35564
GHSA-cqjv-c8hw-93x7
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Ancillary Function Driver (AFD.sys) for WinSock allows an authenticated low-privileged user to gain SYSTEM-level access through a use-after-free condition. The flaw was reported by Microsoft (MSRC) and carries a CVSS 7.8 score with high impact across confidentiality, integrity, and availability. No public exploit identified at time of analysis, though the AFD.sys driver has a long history of similar bugs being weaponized post-disclosure.
Technical ContextAI
AFD.sys is the kernel-mode Ancillary Function Driver that backs the user-mode Winsock (ws2_32.dll) API on Windows, brokering socket operations between applications and the TCP/IP stack. The root cause is CWE-122 (heap-based buffer overflow), though the description specifies a use-after-free - indicating that AFD.sys frees a heap-allocated object but retains or reuses a stale pointer, allowing controlled memory corruption in the kernel pool. AFD.sys is reachable from any user-mode process via standard Winsock calls, making it a high-value attack surface that has been repeatedly targeted (e.g., CVE-2023-21768, CVE-2024-38193) for local privilege escalation.
RemediationAI
Apply the Microsoft security update referenced in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45638 as soon as it is available for your Windows build; exact patch KB numbers should be retrieved from that advisory since they were not included in the provided data. As a compensating control until patching, restrict local interactive and remote-shell access to Windows hosts to trusted administrators only, since exploitation requires local code execution context - this is a meaningful mitigation on servers but largely impractical on user workstations. Application allowlisting (Windows Defender Application Control / AppLocker) can block unsigned exploit binaries from running, with the trade-off of operational overhead for software changes; AFD.sys itself cannot be safely disabled because Winsock depends on it.
More in Windows 10 1607
View allWindows MSHTML component contains a remote code execution vulnerability that allows attackers to craft malicious ActiveX
<p>A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged fi
Windows MSDT (Microsoft Support Diagnostic Tool) allows remote code execution when called via the ms-msdt URL protocol f
The Windows VBScript engine contains a remote code execution vulnerability in object handling that allows full system co
Windows Print Spooler Remote Code Execution Vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no auth
Windows Search Remote Code Execution Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely explo
Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour
Windows Kernel contains a TOCTOU race condition vulnerability allowing local privilege escalation, exploited by the OilR
An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in
An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in
Windows Internet Shortcut Files (.url) contain an external control vulnerability (CVE-2025-33053, CVSS 8.8) that enables
Elevation of privilege in the Windows Win32k kernel-mode driver allows a local, low-privileged attacker to escalate to S
Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Denial Of Service
View allShare
External POC / Exploit Code
Leaving vuln.today