Patch tracker / KB5126836
KB5126836: Windows Server 2012 R2 Security Update (October 2026)
KB5126836 is a Critical security update for Windows Server 2012 R2, released 2026-10-13. It closes 649 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 tenth largest of the 75 updates Microsoft shipped that month, by CVEs closed.
Update summary
Fixes 649 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). This update fixes an actively-exploited (CISA KEV) vulnerability.
Microsoft documents 1 known issue with this update.
- USB audio devices might fail to start or produce no sound
Senserva AI Opinion and rich prompt for KB5126836
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5126836
- Released
- 2026-10-13
- Last changed
- 2026-10-13
- Changes tracked
- 1
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.
Check if KB5126836 is installed
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Known issues, from Microsoft
Quoted from Microsoft's support article for KB5126836 (checked 2026-10-13). Verify against the article before acting.
USB audio devices might fail to start or produce no sound
Symptoms
After installing the September 8, 2026, Windows security update (KB5124012), some USB Audio Class 1.0 devices might fail to start or produce audio. Affected devices might experience one or more of the following symptoms:
The device displays an error in Device Manager: "This device cannot start (Code 10).”
No audio output.
Volume controls are unresponsive or remain at zero.
Sound settings are unresponsive or unavailable.
Some devices might function in standard stereo configurations but fail when using multichannel audio features, including 8-channel or 3D audio modes. Some customers have reported that they're able to restore audio in these cases by switching to 2-channel mode.
This issue is limited to USB Audio Class 1.0 devices.
Resolution
This issue is partially resolved in the out-of-band (OOB) update released on September 14, 2026, (KB5129243) . This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes. Microsoft is working to address the other symptoms and will provide more information when it is available.
IT administrators who need an immediate workaround for the symptoms not addressed yet by the OOB update should contact Microsoft Support for Business for assistance.
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.
What the press says about this update
Trusted-source coverage of the CVEs this update fixes, pulled live from their own feeds.
Scope and sources
- Affected products
- Also released in October 2026
KB5099444
186 CVEs · Critical · exploitedKB5099445
175 CVEs · Critical · exploitedKB5099535
262 CVEs · Critical · exploitedKB5099536
390 CVEs · Critical · exploitedKB5099538
313 CVEs · Critical · exploitedKB5099539
315 CVEs · Critical · exploitedKB5099540
327 CVEs · Critical · exploitedKB5101649
384 CVEs · Critical · exploitedThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.