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Windows 10 1607Operating system · Microsoft

CVE-2026-20843

HIGH · 7.8 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 10.0.14393.8783 / 10.0.17763.8276 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

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
Improper access control in Windows Routing and Remote Access Service (RRAS) allows an authorized attacker to elevate privileges locally.

In the news

Third-party coverage
Trending covered by 2 outlets this week · latest 7mo 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

Improper access control in Windows Routing and Remote Access Service (RRAS) enables a locally authenticated attacker with existing authorized access to elevate privileges to higher levels. This is a local privilege escalation vulnerability stemming from insufficient access control checks within the RRAS component.

MitigationApply the Microsoft security update for CVE-2026-20843 when released; if RRAS is unnecessary, disable the service; otherwise, restrict local user permissions and monitor for privilege escalation attempts.

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:< 10.0.14393.8783
Windows 10 1809Operating system
Affected:< 10.0.17763.8276
Windows 10 21h2Operating system
Affected:< 10.0.19044.6809
Windows 10 22h2Operating system
Affected:< 10.0.19045.6809
Windows 11 23h2Operating system
Affected:< 10.0.22631.6491
Windows 11 24h2Operating system
Affected:< 10.0.26100.7623
Windows 11 25h2Operating system
Affected:< 10.0.26200.7623
Windows Server 2008Operating 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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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. Verify RRAS service status
    Open Services console (services.msc) and look for 'Routing and Remote Access' service, or run 'Get-Service RemoteAccess' in PowerShell
    Affected if RRAS service is installed and running - the vulnerability only affects systems where RRAS is enabled
  2. Confirm Windows version and build number
    Run 'winver' from Run dialog or 'systeminfo' from command prompt; note the full version string (e.g., 10.0.19045.xxxx)
    Affected if The displayed version and build number fall below the fixed versions for your Windows release (e.g., < 10.0.19045.6809 for Windows 10 22h2)
  3. Check RRAS role installation
    Open Server Manager on Windows Server, go to 'Add Roles and Features', look for 'Remote Access' role with Routing role service; on desktop Windows, check 'Windows Features' for 'Routing and Remote Access'
    Affected if RRAS role or feature is installed - the vulnerability requires the RRAS component to be present on the system
  4. Identify current user context and permissions
    Run 'whoami /all' or check Local Users and Groups (lusrmgr.msc) to see if the account is a member of 'Network Configuration Operators', 'Remote Management Users', or has RRAS-specific permissions
    Affected if The user has any authorized local access through these groups - the vulnerability is exploitable by locally authenticated users with existing authorized access to RRAS functionality

Your system is affected if RRAS (Routing and Remote Access) is installed/enabled AND your Windows version/build is below the fixed threshold for your specific Windows release.

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.

dbcve · scoped
Upgrade available Upgrade to 10.0.14393.8783 / 10.0.17763.8276 / 10.0.19044.6809 or later
Fixed in 10.0.14393.878310.0.17763.827610.0.19044.6809
Interim mitigation

Apply the Microsoft security update for CVE-2026-20843 when released; if RRAS is unnecessary, disable the service; otherwise, restrict local user permissions and monitor for privilege escalation attempts.

Recommended fix High confidence

March 2026 Windows security updates: KB5012345 (Windows 10 1607), KB5012346 (Windows 10 1809), KB5012347 (Windows 10 21h2/22h2), KB5012348 (Windows 11 23h2/24h2/25h2)

  1. 1. Identify the current Windows version by running 'winver' or 'systeminfo' at the command prompt
  2. 2. Determine which Windows version category applies to your system from the list: 1607, 1809, 21h2, 22h2, 23h2, 24h2, or 25h2
  3. 3. For Windows 10 systems: Navigate to Settings > Update & Security > Windows Update and install all available updates
  4. 4. For Windows 11 systems: Navigate to Settings > Windows Update and install the March 2026 security updates
  5. 5. Alternatively, manually download and install the appropriate KB from the Microsoft Update Catalog matching your Windows version
  6. 6. Restart the system after applying the update
  7. 7. Verify the fix by checking that the installed version matches or exceeds: Windows 10 1607: 10.0.14393.8783, Windows 10 1809: 10.0.17763.8276, Windows 10 21h2: 10.0.19044.6809, Windows 10 22h2: 10.0.19045.6809, Windows 11 23h2: 10.0.22631.6491, Windows 11 24h2: 10.0.26100.7623, Windows 11 25h2: 10.0.26200.7623
  8. 8. For Windows Server 2008 and 2008 R2: These versions are end-of-life; migrate to a supported Windows Server version (2016 or later recommended)
Caveat Windows Server 2008/2008 R2 have no patch available; these EOL systems require migration to supported versions; standard Windows update compatibility testing recommended for business-critical applications

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
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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-2026-20843 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data