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Windows SMB Client EUVDEUVD-2026-56660

| CVE-2026-62799 HIGH
Heap-based Buffer Overflow (CWE-122)
2026-08-11 secure@microsoft.com GHSA-4ffr-gx27-qw7j
7.8
CVSS 3.1 · Vendor: microsoft
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Severity by source

Vendor (microsoft) PRIMARY
7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
7.8 HIGH

Local attack vector with low privileges confirmed by description ('authorized attacker'); AC:L because no special conditions are described; full C/I/A from SYSTEM-level escalation with no scope change.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

3
Analysis Generated
Aug 11, 2026 - 19:19 vuln.today
Patch available
Aug 11, 2026 - 18:19 EUVD
CVE Published
Aug 11, 2026 - 17:18 nvd
HIGH 7.8

DescriptionCVE.org

Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.

AnalysisAI

Local privilege escalation in the Windows SMB Client on Windows 11 version 26H1 enables a low-privileged authorized attacker to gain SYSTEM-level control via a heap-based buffer overflow (CWE-122). The CVSS 7.8 (High) score reflects low attack complexity and no user interaction required once local access is established, with full confidentiality, integrity, and availability impact on the compromised host. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Persist
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Impact
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Vulnerability AssessmentAI

Exploitation Exploitation requires an authorized local user account with at least low privilege (PR:L per CVSS) on a Windows 11 version 26H1 system at build 10.0.28000.0 through 10.0.28000.2703. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, score 7.8) characterizes this as a high-severity local privilege escalation: low attack complexity and no user interaction needed mean that once an attacker has local code execution, escalation to SYSTEM is technically straightforward. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Apply the Microsoft security update that advances Windows 11 version 26H1 to build 10.0.28000.2704 or later via Windows Update, Windows Server Update Services (WSUS), or the Microsoft Update Catalog; the authoritative advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62799. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory all Windows 11 version 26H1 systems using Active Directory or endpoint detection tools to quantify patch scope. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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EUVD-2026-56660 vulnerability details – vuln.today

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