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CVE-2026-62811 Microsoft CVE debrief

A heap-based buffer overflow in Windows HTTP.sys allows an authorized attacker to elevate privileges locally. Multiple Windows versions are affected, including Windows 11 and Windows Server. This vulnerability, tracked as CVE-2026-62811, is a high-severity issue that requires immediate attention from system administrators and security teams. The affected products include Windows 11 version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2022, Windows Server 2025, and Windows Server 2025 (Server Core installation). The vulnerability allows for local privilege escalation, making it essential for organizations to assess their exposure,

Vendor
Microsoft
Product
Windows 11 version 23H2
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-11
Original CVE updated
2026-10-08
Advisory published
2026-08-11
Advisory updated
2026-10-08

Who should care

System administrators and security teams responsible for Windows systems, particularly those using Windows 11 and Windows Server, should assess exposure and apply patches to prevent local privilege escalation.

Why it matters

CVE-2026-62811 is a high-severity vulnerability in Windows HTTP.sys that allows local privilege escalation. System administrators and security teams should assess exposure and apply patches immediately to prevent exploitation.

  • Local privilege escalation is possible for authorized attackers
  • Patching is required to prevent exploitation
  • System administrators should verify and apply patches for affected Windows versions
  • Monitoring system logs for potential exploitation attempts is recommended

Technical summary

The vulnerability is caused by a heap-based buffer overflow in Windows HTTP.sys, which allows an authorized attacker to elevate privileges locally. The affected products include Windows 11 version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2022, Windows Server 2025, and Windows Server 2025 (Server Core installation).

Defensive priority

Apply patches immediately for Windows 11 and Windows Server systems to prevent local privilege escalation.

Recommended defensive actions

  • Apply patches for Windows 11 version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, and Windows 11 version 26H1
  • Apply patches for Windows Server 2022, Windows Server 2025, and Windows Server 2025 (Server Core installation)
  • Verify and apply patches for other affected Windows versions
  • Review system configurations and ensure proper access controls are in place
  • Monitor system logs for potential exploitation attempts

Evidence notes

The CVE record and source item provide details on the vulnerability. The NVD entry is currently not provided. The vulnerability is caused by a heap-based buffer overflow in Windows HTTP.sys, which allows an authorized attacker to elevate privileges locally. System administrators and security teams should assess exposure and apply patches immediately to prevent exploitation. The affected products include Windows 11 version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows

Sources and references

Verified primary and authoritative sources

  • CVE-2026-62811 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-62811

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

  • CVE-2026-62811 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-62811

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

Supplemental references

  • Windows HTTP.sys Elevation of Privilege Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/62xxx/CVE-2026-62811.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62811

    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.