SB2026061140 - Multiple vulnerabilities in Microsoft Windows Ancillary Function Driver for WinSock
Published: June 11, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 7 vulnerabilities.
1) Use-after-free (CVE-ID: CVE-2026-34335)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in Windows Ancillary Function Driver for WinSock. A local user can win a race condition and gain elevated privileges on the target system.
2) Use-after-free (CVE-ID: CVE-2026-42911)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in Windows Ancillary Function Driver for WinSock. A local user can win a race condition and gain elevated privileges on the target system.
3) Heap-based buffer overflow (CVE-ID: CVE-2026-45638)
CWE-ID: CWE-122 - Heap-based Buffer Overflow
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to escalate privileges on the target system.
The vulnerability exists due to a boundary error in Windows Ancillary Function Driver for WinSock. A local user can pass specially crafted data to the application, trigger a heap-based buffer overflow and gain elevated privileges on the system.
4) Race condition (CVE-ID: CVE-2026-45603)
CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a race condition in Windows Ancillary Function Driver for WinSock. A local user can exploit the race and gain unauthorized access to sensitive information and escalate privileges on the system.
5) Use-after-free (CVE-ID: CVE-2026-45596)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in Windows Ancillary Function Driver for WinSock. A local user can win a race condition and gain elevated privileges on the target system.
6) Race condition (CVE-ID: CVE-2026-45598)
CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a race condition in Windows Ancillary Function Driver for WinSock. A local user can exploit the race and gain unauthorized access to sensitive information and escalate privileges on the system.
7) Race condition (CVE-ID: CVE-2026-45601)
CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a race condition in Windows Ancillary Function Driver for WinSock. A local user can exploit the race and gain unauthorized access to sensitive information and escalate privileges on the system.
Remediation
Install update from vendor's website.
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34335
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42911
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45638
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45603
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45596
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45598
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45601