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Windows 10 1607Operating system · Microsoft

CVE-2026-54995

CRITICAL · 9.8 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 10.0.14393.9339 / 10.0.17763.9020 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Use after free in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over a network.

In the news

Third-party coverage
Trending covered by 1 outlet this week · latest 1mo ago

Surfaced from public web coverage — external links open in a new tab.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A use-after-free vulnerability exists in the Reliable Multicast Transport Driver (RMCAST) that allows an unauthenticated remote attacker to execute arbitrary code. The vulnerability involves improper memory management where memory is accessed after being freed, leading to potential code execution via controlled memory corruption.

MitigationApply vendor-supplied patches for RMCAST driver, disable RMCAST if not required, and implement network segmentation to limit exposure to untrusted networks given the network-exploitable nature of this critical flaw.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 1607Operating system
Affected:< 10.0.14393.9339
Windows 10 1809Operating system
Affected:< 10.0.17763.9020
Windows 10 21h2Operating system
Affected:< 10.0.19044.7548
Windows 10 22h2Operating system
Affected:< 10.0.19045.7548
Windows 11 24h2Operating system
Affected:< 10.0.26100.8875
Windows 11 25h2Operating system
Affected:< 10.0.26200.8875
Windows 11 26h1Operating system
Affected:< 10.0.28000.2525
Windows Server 2012Operating system
Affected:all versions= r2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Windows version and build number
    Open Command Prompt and run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the exact Windows version and build number
    Affected if The build number falls below any of these thresholds: 14393.9339 (Win10 1607), 17763.9020 (Win10 1809), 19044.7548 (Win10 21h2), 19045.7548 (Win10 22h2), 26100.8875 (Win11 24h2), 26200.8875 (Win11 25h2), 28000.2525 (Win11 26h1), or if running Windows Server 2012/R2 (all versions)
  2. Confirm RMCAST driver is present
    Run 'sc query rmcast' in Command Prompt to query the Reliable Multicast Transport Driver service status, or use 'driverquery /v | findstr -i rmcast' to list driver details
    Affected if The RMCAST driver (rmcast.sys) is found on the system, indicating the vulnerable component is installed
  3. Verify RMCAST driver is running or set to start
    Check service configuration with 'sc qc rmcast' for the startup type, and 'sc queryex rmcast' for current running status
    Affected if The service startup type is not DISABLED, meaning the driver could be loaded into memory making exploitation possible
  4. Check RMCAST driver file version
    Navigate to C:\Windows\System32\drivers\rmcast.sys (if present) and right-click properties to view Version tab, or run 'powershell (Get-Item C:\Windows\System32\drivers\rmcast.sys).VersionInfo'
    Affected if The driver file exists and its version is lower than the patched build, or on Windows Server 2012/R2 any version indicates the vulnerable code path

The environment is affected if running an unpatched Windows version within the affected ranges AND the RMCAST driver is present and not disabled on the system.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 10.0.14393.9339 / 10.0.17763.9020 / 10.0.19044.7548 or later
Fixed in 10.0.14393.933910.0.17763.902010.0.19044.7548
Interim mitigation

Apply vendor-supplied patches for RMCAST driver, disable RMCAST if not required, and implement network segmentation to limit exposure to untrusted networks given the network-exploitable nature of this critical flaw.

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing12.0 h
  • Review / QA6.0 h
28.0 hours of engineering $4,800
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,680.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54995 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data