Patch tracker / CVE reference / CVE-2025-64666

CVE-2025-64666

High severity Microsoft vulnerability, CVSS 7.5. Fixed by 4 Microsoft security updates.

High

Risk summary

CVSS base
7.5
EPSS exploit probability
<1%
Severity
High

Exploitation and severity

Not in the CISA KEV catalog. EPSS exploit probability <1%. CVSS 7.5 (High).

This CVE is among the lower half of tracked Microsoft CVEs by EPSS exploit probability.

What to do

Moderate priority: schedule it in your normal patch cycle. In Intune or Defender, confirm whether the fixing updates KB5071873, KB5071874, KB5071875, KB5071876 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Official patch for CVE-2025-64666

Apply the Microsoft security updates below to fix CVE-2025-64666. Each KB page links to the Microsoft Update Catalog download for every affected product.

KB5071873KB5071874KB5071875KB5071876

Affected products

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

Authoritative references

NVD detailMicrosoft MSRCFIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.

Sponsored by SenservaMicrosoft 365, Intune, Defender, and Entra ID security and compliance, with automated remediation and Trustworthy AI.Scan free
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.