EUVD-2026-56393
GHSA-w863-jvv5-xfq6
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Adjacent vector matches PGM multicast protocol scope; PR:N and UI:N confirmed by protocol-level unauthenticated access; full C/I/A triad from kernel-level code execution with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over an adjacent network.
AnalysisAI
Heap-based buffer overflow in the Windows Reliable Multicast Transport (RMCAST) kernel driver enables unauthenticated adjacent-network attackers to execute arbitrary code at kernel privilege level across a broad range of Windows desktop and server releases, from Server 2012 through Windows 11 version 26H1. The CVSS 8.8 rating reflects the zero-credential, zero-interaction exploitation path, constrained only by the requirement for network adjacency. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to occupy an adjacent network position - specifically the same LAN broadcast domain, VLAN, or a subnet reachable via IP multicast routing - as the vulnerable Windows host; direct internet-based exploitation is not possible unless multicast routing is deliberately configured to forward PGM traffic to the target, which is non-default. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 8.8 score is well-supported by the attacker-favorable combination of no required privileges, no user interaction, low attack complexity, and full confidentiality, integrity, and availability impact. … 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 via Windows Update, WSUS, or Microsoft Update Catalog, targeting the following minimum fixed builds: Windows 10 21H2 to 10.0.19044.7663 or later; Windows 10 22H2 to 10.0.19045.7663 or later; Windows 10 1607 and Windows Server 2016 to 10.0.14393.9418 or later; Windows 10 1809 and Windows Server 2019 to 10.0.17763.9115 or later; Windows Server 2022 to 10.0.20348.5499 or later; Windows 11 23H2 to 10.0.22631.7517 or later; Windows 11 24H2 and 25H2 to 10.0.26100.9168 or later; Windows 11 26H1 to 10.0.28000.2704 or later; Windows Server 2025 to 10.0.26100.33296 or later; Windows Server 2012 to 6.2.9200.26279 or later; Windows Server 2012 R2 to 6.3.9600.23337 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: inventory all Windows Server 2012 and later, plus Windows 10-11 systems, to identify your exposure (affected systems range from Server 2012 through Windows 11 version 26H1). …
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External POC / Exploit Code
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