EUVD-2026-44022
GHSA-w75j-4mxv-mw59
Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Network-reachable and unauthenticated with no interaction (AV:N/PR:N/UI:N), but a kernel use-after-free race gives AC:H; kernel-level RCE yields full C:H/I:H/A:H.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over a network.
AnalysisAI
Remote code execution in the Windows Reliable Multicast Transport Driver (RMCAST) lets an unauthenticated network attacker trigger a use-after-free (CWE-416) and run arbitrary code on a broad range of Windows 10, Windows 11, and Windows Server systems (Server 2012 through Server 2025). Rated CVSS 8.1, the flaw carries high impact to confidentiality, integrity, and availability but requires winning a race condition (AC:H), and no public exploit identified at time of analysis. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the target Windows host to have the Reliable Multicast Transport Driver (RMCAST/PGM) active and reachable so the attacker can deliver crafted multicast transport packets - PGM reliable multicast is not enabled in default Windows configurations and is typically present only where applications such as MSMQ multicast are in use, which sharply limits the exposed population. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H = 8.1) describes a network-reachable, unauthenticated, no-interaction bug with full CIA impact, but the High attack complexity is the key tempering factor: reliably winning the use-after-free race and defeating kernel mitigations (KASLR, heap hardening) is non-trivial, which is why the score is 8.1 rather than 9.8. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker on a network segment where a Windows host has RMCAST/PGM listening sends a crafted sequence of reliable-multicast transport packets designed to force the driver to free a buffer that is still referenced, then races to reallocate that freed kernel memory with attacker-controlled data. Winning the race (AC:H) lets the dangling pointer be dereferenced into attacker content, yielding kernel-level code execution without authentication or user interaction. … |
| Remediation | Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-54995 for your specific Windows or Windows Server build as listed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54995, prioritizing internet- or untrusted-network-reachable hosts. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all affected Windows systems in your environment (Windows 10, 11, Server 2012-2025) and confirm patch availability from Microsoft for the RMCAST driver. …
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External POC / Exploit Code
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