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CVE-2026-70575 Microsoft CVE debrief

A null pointer dereference vulnerability in Windows Schannel allows an authorized attacker to deny service over a network. This medium-severity vulnerability affects multiple versions of Windows 11 and Windows Server. Microsoft has released patches for this vulnerability. The vulnerability can be triggered by a specially crafted network request, which can cause a denial of service. Affected systems should be patched immediately to prevent exploitation. The CVE Program and NVD provide official records of this vulnerability.

Vendor
Microsoft
Product
Windows 11 version 23H2
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-10-08
Advisory published
2026-09-08
Advisory updated
2026-10-08

Who should care

Defenders responsible for Windows systems, especially those exposed to network attacks, should assess exposure and apply patches. System administrators and security teams should review the vulnerability details and patch affected systems. Network defenders should monitor for unusual network activity and review compensating controls. Vulnerability management teams should prioritize patching affected systems.

Why it matters

CVE-2026-70575 is a medium-severity vulnerability in Windows Schannel that allows an authorized attacker to deny service. Defenders should assess exposure, especially for systems exposed to network attacks, and apply patches immediately.

  • Denial of service over a network
  • Potential disruption to critical systems
  • Requires patching for affected versions
  • Network attack surface assessment necessary

Technical summary

A null pointer dereference in Windows Schannel allows an authorized attacker to deny service over a network. This vulnerability affects Windows 11 versions 23H2, 24H2, 25H2, 26H1, and Windows Server 2022, 2025. The vulnerability can be triggered by a specially crafted network request. Microsoft has released patches for affected versions. Defenders should assess exposure and apply patches immediately.

Defensive priority

Apply patches immediately, especially for systems exposed to network attacks

Recommended defensive actions

  • Apply patches for affected Windows 11 and Windows Server versions
  • Review network exposure for affected systems
  • Monitor for unusual network activity

Evidence notes

The CVE Program and NVD provide official records of this vulnerability. Microsoft has released a patch for this issue. The vulnerability was reported by a security researcher and patched by Microsoft. The patch is available for affected versions of Windows 11 and Windows Server. Defenders should verify patch deployment and monitor for unusual network activity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-70575 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-70575

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

  • CVE-2026-70575 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-70575

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

Supplemental references

  • Windows Schannel Denial of Service Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/70xxx/CVE-2026-70575.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70575

    Supplemental source - vendor-advisory, patch

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.