Patch tracker / KB5123066

KB5123066: Windows Server 2012 R2 Security Update (September 2026)

KB5123066 is a Critical security update for Windows Server 2012 R2, released 2026-09-08. It closes 418 CVEs with a maximum CVSS of 9.8. At least one of them is actively exploited (CISA KEV), so this is a deploy-first update. It is the ninth largest of the 69 updates Microsoft shipped that month, by CVEs closed.

Update summary

CriticalCISA KEV
2026-09-08
Released
418
CVEs fixed
9.8
Max CVSS v3
Critical
Severity
Deploy now
This update fixes vulnerabilities confirmed exploited in the wild.

Fixes 418 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 3.6%. Among the top half of tracked Microsoft updates by EPSS exploit probability.

Senserva found thisread these before you deploy broadly

Microsoft documents 1 known issue with this update.

  • Remote Desktop Services might stop responding after September 2026 security update

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5123066Microsoft support article
Senserva AI Opinion and rich prompt for KB5123066

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

Full tracking and change history for KB5123066

Released
2026-09-08
Last changed
2026-09-26
Changes tracked
5

Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.

Senserva Watchevery change we have recorded for this one
What changed, and when

Microsoft revised KB5123066 on 2026-09-12: CVEs fixed 417 to 418.

  • 2026-09-12 CVEs fixed 417 to 418

Recorded by Senserva on the dates shown, from the MSRC release feed. This is what moved and when, which neither the vendor advisory nor NVD publishes.

Check if KB5123066 is installed

Elevated PowerShell. No output means it is not installed.

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5123066 (checked 2026-09-27). Verify against the article before acting.

Remote Desktop Services might stop responding after September 2026 security update

Symptoms

After installing the September 2026 Windows security update, some organizations might experience issues with Remote Desktop Services (RDS).

In some environments, RDS might become unstable, resulting in RDP connections failing after several minutes, sign-in issues, or servers hanging at "Please wait for the Remote Desktop Configuration". Related tools, including Microsoft Management Console (MMC), RDS Licensing Diagnoser, and File Explorer might also become unresponsive. Additionally, the Windows Update page might stop responding and continuously display a loading indicator.

Note

This issue does not affect Windows 365 or Azure Virtual Desktop.

Resolution

This issue is resolved in Windows updates released on and after September 14, 2026 such as KB5129243 . We recommend you install the latest Windows update for your device as it contains important improvements and issue resolutions, including this one.

CVEs fixed by this update

Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.

CVESeverityCVSSEPSSExploited
CVE-2026-85880High9.83.6%KEV
CVE-2026-68830Critical9.83.6%No
CVE-2026-68831Critical9.83.6%No
CVE-2026-68839Critical9.83.6%No
CVE-2026-68843Critical9.83.6%No
CVE-2026-68851Critical9.83.6%No
CVE-2026-68852Critical9.83.6%No
CVE-2026-68874Critical9.83.6%No
CVE-2026-68881Critical9.83.6%No
CVE-2026-68891Critical9.83.6%No
CVE-2026-68895Critical9.83.6%No
CVE-2026-69276Critical9.83.6%No
CVE-2026-69286Critical9.83.6%No
CVE-2026-69288Critical9.83.6%No
CVE-2026-69308Critical9.83.6%No
CVE-2026-69317Critical9.83.6%No
CVE-2026-69318Critical9.83.6%No
CVE-2026-69321Critical9.83.6%No
CVE-2026-69343Critical9.83.6%No
CVE-2026-69345Critical9.83.6%No
CVE-2026-69349Critical9.83.6%No
CVE-2026-69351Critical9.83.6%No
CVE-2026-69353Critical9.83.6%No
CVE-2026-69367Critical9.83.6%No
CVE-2026-69369Critical9.83.6%No
CVE-2026-69372Critical9.83.6%No
CVE-2026-69376Critical9.83.6%No
CVE-2026-69381Critical9.83.6%No
CVE-2026-69405Critical9.83.6%No
CVE-2026-69406Critical9.83.6%No
CVE-2026-69408Critical9.83.6%No
CVE-2026-69416Critical9.83.6%No
CVE-2026-69431Critical9.83.6%No
CVE-2026-69453Critical9.83.6%No
CVE-2026-69457Critical9.83.6%No
CVE-2026-69463Critical9.83.6%No
CVE-2026-69474Critical9.83.6%No
CVE-2026-69483Critical9.83.6%No
CVE-2026-69491Critical9.83.6%No
CVE-2026-69493Critical9.83.6%No
CVE-2026-69496Critical9.83.6%No
CVE-2026-69504Critical9.83.6%No
CVE-2026-69525Critical9.83.6%No
CVE-2026-69527Critical9.83.6%No
CVE-2026-69548Critical9.83.6%No
CVE-2026-69552Critical9.83.6%No
CVE-2026-69554Critical9.83.6%No
CVE-2026-69568Critical9.83.6%No
CVE-2026-69569Critical9.83.6%No
CVE-2026-69572Critical9.83.6%No
CVE-2026-69579Critical9.83.6%No
CVE-2026-69590Critical9.83.6%No
CVE-2026-69595Critical9.83.6%No
CVE-2026-69609Critical9.83.6%No
CVE-2026-69616Critical9.83.6%No
CVE-2026-69618Critical9.83.6%No
CVE-2026-69627Critical9.83.6%No
CVE-2026-69637Critical9.83.6%No
CVE-2026-69672Critical9.83.6%No
CVE-2026-69679Critical9.83.6%No
CVE-2026-69684Critical9.83.6%No
CVE-2026-69713Critical9.83.6%No
CVE-2026-69715Critical9.83.6%No
CVE-2026-69723Critical9.83.6%No
CVE-2026-69730Critical9.83.6%No
CVE-2026-69768Critical9.83.6%No
CVE-2026-69769Critical9.83.6%No
CVE-2026-69770Critical9.83.6%No
CVE-2026-69808Critical9.83.6%No
CVE-2026-69819Critical9.83.6%No
CVE-2026-69824Critical9.83.6%No
CVE-2026-69829Critical9.83.6%No
CVE-2026-69832Critical9.83.6%No
CVE-2026-69845Critical9.83.6%No
CVE-2026-69853Critical9.83.6%No
CVE-2026-69878Critical9.83.6%No
CVE-2026-69895Critical9.83.6%No
CVE-2026-70091Critical9.83.6%No
CVE-2026-70145Critical9.83.6%No
CVE-2026-70290Critical9.83.6%No
CVE-2026-70296Critical9.83.6%No
CVE-2026-70582Critical9.83.6%No
CVE-2026-71338Critical9.83.6%No
CVE-2026-71341Critical9.83.6%No
CVE-2026-72931Critical9.83.6%No
CVE-2026-72937Critical9.83.6%No
CVE-2026-72950Critical9.83.6%No
CVE-2026-72966Critical9.83.6%No
CVE-2026-72979Critical9.83.6%No
CVE-2026-72982Critical9.83.6%No
CVE-2026-72983Critical9.83.6%No
CVE-2026-73009Critical9.83.6%No
CVE-2026-73019Critical9.83.6%No
CVE-2026-73025Critical9.83.6%No
CVE-2026-77491Critical9.83.6%No
CVE-2026-77492Critical9.83.6%No
CVE-2026-77493Critical9.83.6%No
CVE-2026-77887Critical9.83.6%No
CVE-2026-77891Critical9.83.6%No
CVE-2026-78445Critical9.83.6%No
CVE-2026-78446Critical9.83.6%No
CVE-2026-78508Critical9.83.6%No
CVE-2026-78516Critical9.83.6%No
CVE-2026-62706High8.83.6%No
CVE-2026-68828High8.83.6%No
CVE-2026-69266High8.83.6%No
CVE-2026-69291High8.83.6%No
CVE-2026-69334High8.83.6%No
CVE-2026-69360High8.83.6%No
CVE-2026-69434High8.83.6%No
CVE-2026-69461High8.83.6%No
CVE-2026-69494High8.83.6%No
CVE-2026-69495High8.83.6%No
CVE-2026-69499High8.83.6%No
CVE-2026-69511High8.83.6%No
CVE-2026-69518High8.83.6%No
CVE-2026-69547High8.83.6%No
CVE-2026-69551High8.83.6%No
CVE-2026-69598High8.83.6%No
CVE-2026-69601High8.83.6%No
CVE-2026-69603High8.83.6%No
CVE-2026-69619High8.83.6%No
CVE-2026-69628High8.83.6%No
CVE-2026-69669High8.83.6%No
CVE-2026-69676High8.83.6%No
CVE-2026-69681High8.83.6%No
CVE-2026-69712High8.83.6%No
CVE-2026-69714High8.83.6%No
CVE-2026-69717High8.83.6%No
CVE-2026-69772High8.83.6%No
CVE-2026-69860High8.83.6%No
CVE-2026-70203High8.83.6%No
CVE-2026-70586High8.83.6%No
CVE-2026-71336High8.83.6%No
CVE-2026-71352High8.83.6%No
CVE-2026-72933High8.83.6%No
CVE-2026-72959High8.83.6%No
CVE-2026-72986High8.83.6%No
CVE-2026-73012High8.83.6%No
CVE-2026-73013High8.83.6%No
CVE-2026-73016High8.83.6%No
CVE-2026-73018High8.83.6%No
CVE-2026-73023High8.83.6%No
CVE-2026-77495High8.83.6%No
CVE-2026-77504High8.83.6%No
CVE-2026-80096High8.83.6%No
CVE-2026-81955High8.83.6%No
CVE-2026-83992High8.83.6%No
CVE-2026-83996High8.83.6%No
CVE-2026-69479High8.43.6%No
CVE-2026-69638High8.43.6%No
CVE-2026-69325High8.13.6%No
CVE-2026-69438High8.13.6%No
CVE-2026-69510High8.13.6%No
CVE-2026-69524High8.13.6%No
CVE-2026-69546High8.13.6%No
CVE-2026-69620High8.13.6%No
CVE-2026-69680High8.13.6%No
CVE-2026-69732High8.13.6%No
CVE-2026-69782High8.13.6%No
CVE-2026-69786High8.13.6%No
CVE-2026-69813High8.13.6%No
CVE-2026-69827High8.13.6%No
CVE-2026-69989High8.13.6%No
CVE-2026-70342High8.13.6%No
CVE-2026-70563High8.13.6%No
CVE-2026-70570High8.13.6%No
CVE-2026-72981High8.13.6%No
CVE-2026-72987High8.13.6%No
CVE-2026-77505High8.13.6%No
CVE-2026-78449High8.13.6%No
CVE-2026-68827High8.03.6%No
CVE-2026-68834High8.03.6%No
CVE-2026-68838High8.03.6%No
CVE-2026-68876High8.03.6%No
CVE-2026-68878High8.03.6%No
CVE-2026-68880High8.03.6%No
CVE-2026-68894High8.03.6%No
CVE-2026-69271High8.03.6%No
CVE-2026-69301High8.03.6%No
CVE-2026-69332High8.03.6%No
CVE-2026-69346High8.03.6%No
CVE-2026-69371High8.03.6%No
CVE-2026-69412High8.03.6%No
CVE-2026-69418High8.03.6%No
CVE-2026-69423High8.03.6%No
CVE-2026-69427High8.03.6%No
CVE-2026-69458High8.03.6%No
CVE-2026-69462High8.03.6%No
CVE-2026-69481High8.03.6%No
CVE-2026-69505High8.03.6%No
CVE-2026-69623High8.03.6%No
CVE-2026-69643High8.03.6%No
CVE-2026-69807High8.03.6%No
CVE-2026-69847High8.03.6%No
CVE-2026-69876High8.03.6%No
CVE-2026-62810High7.83.6%No
CVE-2026-68832High7.83.6%No
CVE-2026-68841High7.83.6%No
CVE-2026-68845High7.83.6%No
CVE-2026-68848High7.83.6%No
CVE-2026-68875High7.83.6%No
CVE-2026-68885High7.83.6%No
CVE-2026-68888High7.83.6%No
CVE-2026-68890High7.83.6%No
CVE-2026-68892High7.83.6%No
CVE-2026-69265High7.83.6%No
CVE-2026-69269High7.83.6%No
CVE-2026-69270High7.83.6%No
CVE-2026-69277High7.83.6%No
CVE-2026-69283High7.83.6%No
CVE-2026-69284High7.83.6%No
CVE-2026-69289High7.83.6%No
CVE-2026-69290High7.83.6%No
CVE-2026-69295High7.83.6%No
CVE-2026-69307High7.83.6%No
CVE-2026-69312High7.83.6%No
CVE-2026-69324High7.83.6%No
CVE-2026-69368High7.83.6%No
CVE-2026-69389High7.83.6%No
CVE-2026-69407High7.83.6%No
CVE-2026-69420High7.83.6%No
CVE-2026-69421High7.83.6%No
CVE-2026-69424High7.83.6%No
CVE-2026-69426High7.83.6%No
CVE-2026-69432High7.83.6%No
CVE-2026-69445High7.83.6%No
CVE-2026-69450High7.83.6%No
CVE-2026-69455High7.83.6%No
CVE-2026-69475High7.83.6%No
CVE-2026-69509High7.83.6%No
CVE-2026-69532High7.83.6%No
CVE-2026-69538High7.83.6%No
CVE-2026-69541High7.83.6%No
CVE-2026-69561High7.83.6%No
CVE-2026-69571High7.83.6%No
CVE-2026-69576High7.83.6%No
CVE-2026-69582High7.83.6%No
CVE-2026-69584High7.83.6%No
CVE-2026-69585High7.83.6%No
CVE-2026-69592High7.83.6%No
CVE-2026-69604High7.83.6%No
CVE-2026-69608High7.83.6%No
CVE-2026-69612High7.83.6%No
CVE-2026-69685High7.83.6%No
CVE-2026-69687High7.83.6%No
CVE-2026-69691High7.83.6%No
CVE-2026-69707High7.83.6%No
CVE-2026-69709High7.83.6%No
CVE-2026-69731High7.83.6%No
CVE-2026-69758High7.83.6%No
CVE-2026-69785High7.83.6%No
CVE-2026-69821High7.83.6%No
CVE-2026-69841High7.83.6%No
CVE-2026-69844High7.83.6%No
CVE-2026-70289High7.83.6%No
CVE-2026-70564High7.83.6%No
CVE-2026-70574High7.83.6%No
CVE-2026-71334High7.83.6%No
CVE-2026-71343High7.83.6%No
CVE-2026-71345High7.83.6%No
CVE-2026-72927High7.83.6%No
CVE-2026-72944High7.83.6%No
CVE-2026-72948High7.83.6%No
CVE-2026-72957High7.83.6%No
CVE-2026-72965High7.83.6%No
CVE-2026-72967High7.83.6%No
CVE-2026-73024High7.83.6%No
CVE-2026-77503High7.83.6%No
CVE-2026-77904High7.83.6%No
CVE-2026-80075High7.83.6%No
CVE-2026-81355High7.83.6%No
CVE-2026-83995High7.83.6%No
CVE-2026-84000High7.83.6%No
CVE-2026-62759High7.53.6%No
CVE-2026-62813High7.53.6%No
CVE-2026-68887High7.53.6%No
CVE-2026-69329High7.53.6%No
CVE-2026-69342High7.53.6%No
CVE-2026-69428High7.53.6%No
CVE-2026-69514High7.53.6%No
CVE-2026-69539High7.53.6%No
CVE-2026-69607High7.53.6%No
CVE-2026-69631High7.53.6%No
CVE-2026-69688High7.53.6%No
CVE-2026-69706High7.53.6%No
CVE-2026-69761High7.53.6%No
CVE-2026-69793High7.53.6%No
CVE-2026-69803High7.53.6%No
CVE-2026-69852High7.53.6%No
CVE-2026-69929High7.53.6%No
CVE-2026-69930High7.53.6%No
CVE-2026-70065High7.53.6%No
CVE-2026-70124High7.53.6%No
CVE-2026-70587High7.53.6%No
CVE-2026-71330High7.53.6%No
CVE-2026-72932High7.53.6%No
CVE-2026-72943High7.53.6%No
CVE-2026-72954High7.53.6%No
CVE-2026-72978High7.53.6%No
CVE-2026-77494High7.53.6%No
CVE-2026-77498High7.53.6%No
CVE-2026-77499High7.53.6%No
CVE-2026-77501High7.53.6%No
CVE-2026-77502High7.53.6%No
CVE-2026-77886High7.53.6%No
CVE-2026-77888High7.53.6%No
CVE-2026-77889High7.53.6%No
CVE-2026-77890High7.53.6%No
CVE-2026-77893High7.53.6%No
CVE-2026-77895High7.53.6%No
CVE-2026-78523High7.53.6%No
CVE-2026-83989High7.53.6%No
CVE-2026-84001High7.53.6%No
CVE-2026-69347High7.43.6%No
CVE-2026-68835High7.13.6%No
CVE-2026-68846High7.13.6%No
CVE-2026-68889High7.13.6%No
CVE-2026-68893High7.13.6%No
CVE-2026-69272High7.13.6%No
CVE-2026-69274High7.13.6%No
CVE-2026-69296High7.13.6%No
CVE-2026-69305High7.13.6%No
CVE-2026-69313High7.13.6%No
CVE-2026-69336High7.13.6%No
CVE-2026-69337High7.13.6%No
CVE-2026-69338High7.13.6%No
CVE-2026-69340High7.13.6%No
CVE-2026-69357High7.13.6%No
CVE-2026-69364High7.13.6%No
CVE-2026-69366High7.13.6%No
CVE-2026-69396High7.13.6%No
CVE-2026-69451High7.13.6%No
CVE-2026-50349High7.03.6%No
CVE-2026-62694High7.03.6%No
CVE-2026-68840High7.03.6%No
CVE-2026-68897High7.03.6%No
CVE-2026-69275High7.03.6%No
CVE-2026-69287High7.03.6%No
CVE-2026-69292High7.03.6%No
CVE-2026-69309High7.03.6%No
CVE-2026-69310High7.03.6%No
CVE-2026-69311High7.03.6%No
CVE-2026-69319High7.03.6%No
CVE-2026-69331High7.03.6%No
CVE-2026-69335High7.03.6%No
CVE-2026-69341High7.03.6%No
CVE-2026-69362High7.03.6%No
CVE-2026-69385High7.03.6%No
CVE-2026-69394High7.03.6%No
CVE-2026-69404High7.03.6%No
CVE-2026-69410High7.03.6%No
CVE-2026-69413High7.03.6%No
CVE-2026-69441High7.03.6%No
CVE-2026-69466High7.03.6%No
CVE-2026-69468High7.03.6%No
CVE-2026-69473High7.03.6%No
CVE-2026-69488High7.03.6%No
CVE-2026-69492High7.03.6%No
CVE-2026-69500High7.03.6%No
CVE-2026-69560High7.03.6%No
CVE-2026-69564High7.03.6%No
CVE-2026-69567High7.03.6%No
CVE-2026-69573High7.03.6%No
CVE-2026-69578High7.03.6%No
CVE-2026-69581High7.03.6%No
CVE-2026-69600High7.03.6%No
CVE-2026-69610High7.03.6%No
CVE-2026-69613High7.03.6%No
CVE-2026-69621High7.03.6%No
CVE-2026-69630High7.03.6%No
CVE-2026-69645High7.03.6%No
CVE-2026-69692High7.03.6%No
CVE-2026-69779High7.03.6%No
CVE-2026-69817High7.03.6%No
CVE-2026-69834High7.03.6%No
CVE-2026-69838High7.03.6%No
CVE-2026-69859High7.03.6%No
CVE-2026-69911High7.03.6%No
CVE-2026-70283High7.03.6%No
CVE-2026-70562High7.03.6%No
CVE-2026-70565High7.03.6%No
CVE-2026-70568High7.03.6%No
CVE-2026-70585High7.03.6%No
CVE-2026-71333High7.03.6%No
CVE-2026-71342High7.03.6%No
CVE-2026-71351High7.03.6%No
CVE-2026-71353High7.03.6%No
CVE-2026-72930High7.03.6%No
CVE-2026-77894High7.03.6%No
CVE-2026-77905High7.03.6%No
CVE-2026-85360High7.03.6%No
CVE-2026-68833Medium6.83.6%No
CVE-2026-69415Medium6.83.6%No
CVE-2026-69490Medium6.83.6%No
CVE-2026-69566Medium6.83.6%No
CVE-2026-71329Medium6.83.6%No
CVE-2026-71348Medium6.83.6%No
CVE-2026-71349Medium6.83.6%No
CVE-2026-71350Medium6.83.6%No
CVE-2026-72985Medium6.83.6%No
CVE-2026-77892Medium6.83.6%No
CVE-2026-69350Medium6.73.6%No
CVE-2026-69373Medium6.73.6%No
CVE-2026-69449Medium6.73.6%No
CVE-2026-71339Medium6.73.6%No
CVE-2026-72935Medium6.73.6%No
CVE-2026-62762Medium6.53.6%No
CVE-2026-62801Medium6.53.6%No
CVE-2026-68898Medium6.53.6%No
CVE-2026-69297Medium6.53.6%No
CVE-2026-69395Medium6.53.6%No
CVE-2026-69497Medium6.53.6%No
CVE-2026-69624Medium6.53.6%No
CVE-2026-69839Medium6.53.6%No
CVE-2026-72939Medium6.53.6%No
CVE-2026-72942Medium6.53.6%No
CVE-2026-78453Medium6.53.6%No

Scope and sources

Affected products
Also released in September 2026

KB5122871

679 CVEs · Critical · exploited

KB5122876

616 CVEs · Critical · exploited

KB5122878

568 CVEs · Critical · exploited

KB5122880

602 CVEs · Critical · exploited

KB5122882

641 CVEs · Critical · exploited

KB5123065

393 CVEs · Critical · exploited

KB5123099

555 CVEs · Critical · exploited

KB5124008

628 CVEs · Critical · exploited

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5123066 page (Microsoft Support)Microsoft Update CatalogMicrosoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
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