EUVD-2026-43969
GHSA-46c5-ppqr-v898
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Local-only attack requiring a low-privilege authenticated session; confidentiality is high as sensitive data is fully exposed, but no integrity or availability impact applies.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Cleartext transmission of sensitive information in Windows Ancillary Function Driver for WinSock allows an authorized attacker to disclose information locally.
AnalysisAI
Cleartext transmission of sensitive information in the Windows Ancillary Function Driver for WinSock (afd.sys) enables a locally authenticated, low-privilege attacker to intercept or read sensitive data that the driver handles without adequate protection. Affected platforms span Windows 10 (multiple versions), Windows 11, and Windows Server 2012 through 2025 as confirmed by EUVD version data and Microsoft CPE strings. No public exploit has been identified at time of analysis, EPSS is extremely low at 0.21% (11th percentile), and CISA SSVC classifies this as no active exploitation with non-automatable attack paths, positioning this as a low-urgency but meaningful local disclosure risk.
Technical ContextAI
The Windows Ancillary Function Driver for WinSock (afd.sys) is a kernel-mode driver that implements the core Winsock API layer, mediating socket creation, data transmission, and address resolution between user-space applications and the underlying transport stack. CWE-319 (Cleartext Transmission of Sensitive Information) indicates that sensitive data - potentially socket buffer contents, credentials, or application-layer payloads - is passed through this kernel component without encryption or adequate in-transit protection, making it observable to co-resident low-privilege processes. The local attack vector (AV:L) confirms exploitation is confined to the local machine context rather than being remotely triggerable. Affected product strings cover cpe:2.3:a:microsoft:windows_10_version_1607 through cpe:2.3:a:microsoft:windows_server_2012, indicating the flaw spans at least a decade of Windows releases.
RemediationAI
Apply the vendor-released patch via Windows Update or the Microsoft Update Catalog; exact fixed build versions are defined per platform in the EUVD data (e.g., Windows 11 24H2 fixed at 10.0.26100.8875, Windows Server 2025 at 10.0.26100.33158, Windows Server 2022 at 10.0.20348.5386 - consult the full version table in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34346). For systems where immediate patching is not feasible, restrict local interactive logon rights to the minimum required user set using Group Policy (User Rights Assignment: 'Allow log on locally' and 'Allow log on through Remote Desktop Services'), which raises the effective PR bar by limiting who can obtain local access in the first place. Additionally, enforcing application-layer TLS for sensitive communications handled by affected applications reduces the value of any data observable via this flaw - note this mitigates impact rather than the vulnerability itself. Windows Server 2012 and 2012 R2 are past end-of-life and should be prioritized for upgrade or enrolled in Extended Security Updates (ESU); continued reliance on compensating controls for these versions carries elevated long-term risk.
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External POC / Exploit Code
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