EUVD-2026-56365
GHSA-3x6c-wqxm-2hxm
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector and low-privilege requirement match 'authorized attacker' prerequisite; AC:H reflects inherent complexity of reliably exploiting a kernel-mode heap overflow; full C/I/A impact reflects achievable SYSTEM privileges.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.
AnalysisAI
Heap-based buffer overflow in Windows HTTP.sys enables a locally authenticated, low-privileged attacker to escalate privileges on the affected host, likely achieving SYSTEM-level control. The flaw spans a wide range of Windows versions from Server 2012 through Windows 11 26H1, representing substantial enterprise exposure despite requiring initial local access. No public exploit has been identified at time of analysis, and Microsoft has released patched builds across all affected product lines via the MSRC advisory.
Technical ContextAI
HTTP.sys is the Windows kernel-mode HTTP protocol stack, used by IIS, WinRM, and other Windows services for native HTTP handling directly within the kernel. CWE-122 (Heap-based Buffer Overflow) indicates that the vulnerability arises when HTTP.sys writes data beyond the bounds of an allocated kernel heap buffer, corrupting adjacent memory structures. In kernel-mode context, such corruption can be leveraged to overwrite function pointers, security tokens, or other privilege-critical kernel objects, enabling escalation from a low-privileged user to SYSTEM. Affected products as identified by EUVD-2026-56365 span Windows 10 (1607 through 22H2), Windows 11 (23H2 through 26H1), and Windows Server 2012 through Server 2025, including Server Core variants.
RemediationAI
Apply the Microsoft security update via Windows Update or WSUS targeting the fixed builds per affected version - for example, Windows Server 2025 to 10.0.26100.33296, Windows 11 24H2 to 10.0.26100.9168, Windows Server 2022 to 10.0.20348.5499, Windows Server 2019 to 10.0.17763.9115, Windows Server 2016 to 10.0.14393.9418, Windows 10 22H2 to 10.0.19045.7663, and Server 2012/2012R2 to 6.2.9200.26279 and 6.3.9600.23337 respectively. The full advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62753. Prioritize patching systems where low-privileged user sessions are accessible to untrusted parties (e.g., multi-tenant servers, RDS hosts, developer workstations). Where immediate patching is not feasible, restrict local interactive and remote logon rights to the minimum required set of accounts via Group Policy (User Rights Assignment), and deploy Windows Defender for Endpoint or equivalent EDR with alerting on anomalous kernel-level privilege escalation events - noting this monitoring reduces detection time but does not eliminate the vulnerability.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
Leaving vuln.today