EUVD-2026-44015
GHSA-mhhw-8j27-mg72
Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Adjacent-network multicast driver flaw, unauthenticated and no interaction with low complexity (AV:A/AC:L/PR:N/UI:N); kernel code execution yields full C/I/A impact within an unchanged scope.
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
2DescriptionCVE.org
Integer underflow (wrap or wraparound) in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over an adjacent network.
AnalysisAI
Remote code execution in the Windows Reliable Multicast Transport Driver (RMCAST) lets an unauthenticated attacker on the same network segment run arbitrary code by triggering an integer underflow (CWE-191) during multicast message processing. All supported Windows client and server builds from Windows Server 2012 through Windows Server 2025 and Windows 10 1607 through Windows 11 26H1 are affected. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires network adjacency (AV:A) - the attacker must be able to send multicast/PGM packets to the target on the same broadcast domain, VLAN, or subnet, not from an arbitrary internet host - and the target must have the RMCAST/PGM multicast path reachable, which in practice means Message Queuing (MSMQ) or another PGM-based service is installed and listening. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The signals are mostly consistent and point to a genuine priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has gained a foothold on the same LAN or VLAN as a Windows server sends crafted PGM multicast packets to the RMCAST driver, triggering the integer underflow and executing code in the kernel network context without any credentials or user interaction. This is a strong lateral-movement and privilege-gaining primitive after initial access to a subnet; no public POC was identified at time of analysis, so exploitation would currently require original research. |
| Remediation | Patch available per vendor advisory: apply the Microsoft security update for CVE-2026-54982 from the MSRC update guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54982) to every affected client and server SKU, including Server Core; consult that page for the exact KB/build number for each Windows version, as an exact fix version was not included in the supplied data. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: scan your environment to identify all Windows Server 2012-2025 and Windows 10 1607-Windows 11 26H1 systems using asset management or SCCM reporting, and flag domain-joined and internet-facing devices for priority patching. …
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Same weakness CWE-191 – Integer Underflow
View allSame technique Authentication Bypass
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External POC / Exploit Code
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