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PatchSiren cyber security CVE debrief

CVE-2026-33100 Microsoft CVE debrief

The Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability, tracked as CVE-2026-33100, is a high-severity vulnerability that allows an authorized attacker to elevate privileges locally. This vulnerability is particularly concerning for defenders responsible for Windows systems, especially those using Windows 10, Windows 11, and Windows Server. The vulnerability is a use-after-free issue in the Windows Ancillary Function Driver for WinSock. Defenders should prioritize verifying exposure and applying patches to prevent potential exploitation. The CVE record was published on 2026-04-14T16:58:40.062Z and has not been modified since then.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-14
Original CVE updated
2026-10-15
Advisory published
2026-04-14
Advisory updated
2026-10-15

Who should care

Defenders responsible for Windows systems, particularly those using Windows 10, Windows 11, and Windows Server, should assess exposure and apply patches.

Why it matters

CVE-2026-33100 is a high-severity elevation of privilege vulnerability in Windows Ancillary Function Driver for WinSock. Defenders should prioritize verifying exposure and applying patches to prevent potential exploitation.

  • Potential elevation of privileges by authorized attackers
  • Possible disruption to Windows-based systems and services
  • Need for verification of exposure and application of patches
  • Potential impact on Windows Server installations

Technical summary

A use-after-free vulnerability in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally. This vulnerability is particularly concerning for defenders responsible for Windows systems, especially those using Windows 10, Windows 11, and Windows Server. The vulnerability has a CVSS score of 7 and a severity rating of HIGH.

Defensive priority

Defenders should prioritize verifying exposure and applying patches for Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability.

Recommended defensive actions

  • Verify exposure by checking Windows versions and applying patches
  • Assess and apply compensating controls if patches cannot be applied immediately
  • Monitor systems for potential exploitation attempts

Evidence notes

The CVE Program record and NVD vulnerability detail provide information on the vulnerability. Microsoft's official advisory is referenced. The vulnerability has a CVSS score of 7 and a severity rating of HIGH. The NVD entry is currently HIGH. The CVE record was published on 2026-04-14T16:58:40.062Z and has not been modified since then. The source item for CVE-2026-33100 is from cve_program_cvelist_v5.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-33100 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-33100

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-33100 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-33100

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.