Patch tracker / KB5071876

KB5071876

Microsoft security update released 2025-12-09. Fixes 2 CVEs.

High

Download KB5071876

Get the official update for KB5071876. The download and file size for each supported product are on the Microsoft Update Catalog page.

Microsoft Update Catalog: download KB5071876Microsoft support article

Update summary

Released
2025-12-09
CVEs fixed
2
Max CVSS
7.5
Severity
High

Exploitation and severity

Fixes 2 CVEs. Most severe CVSS 7.5 (High). EPSS exploit probability up to <1%.

Among the lower half of tracked Microsoft updates by EPSS exploit probability.

What to do

Moderate priority: schedule it in your normal patch cycle. Senserva flags whether KB5071876 is missing on your devices.

CVEs fixed by this update

CVE-2025-64666CVE-2025-64667

Affected products

  • Microsoft Exchange Server 2016 Cumulative Update 23
  • Microsoft Exchange Server 2019 Cumulative Update 15
  • Microsoft Exchange Server Subscription Edition RTM

References

Microsoft support articleMicrosoft Security Update Guide

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

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Lexicon: the terms on this page
CVE
Common Vulnerabilities and Exposures. A unique ID for one publicly known vulnerability, such as CVE-2025-1234.
KB
Microsoft Knowledge Base article. The identifier for a specific Microsoft update.
KEV
CISA Known Exploited Vulnerabilities. CVEs confirmed exploited in the wild. Fix these first.
CVSS
Common Vulnerability Scoring System. A standardized Severity score from 0 to 10.
EPSS
Exploit Prediction Scoring System. The probability a CVE will be exploited in the next 30 days.
MSRC
Microsoft Security Response Center. Microsoft's Patch Tuesday advisories and KB-to-CVE mapping.
NVD
National Vulnerability Database (NIST). Authoritative CVE metadata and CVSS scores.
Ransomware
The vulnerability is linked to known ransomware activity.