Patch tracker / CVE reference / CVE-2025-21212

CVE-2025-21212

CVE-2025-21212 is a medium severity Microsoft vulnerability with a CVSS score of 6.5. Its EPSS score puts the probability of exploitation in the next 30 days at 24%. Microsoft has shipped the fix: deploy one of the 9 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

Medium

6.5

CVSS

24%

EPSS, 30 days

Medium

Severity

Not in the CISA KEV catalog. EPSS exploit probability 24%. CVSS 6.5 (Medium).

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

Senserva AI Opinion for CVE-2025-21212

Internet Connection Sharing on these Windows 10 1809 and Server 2019 hosts can be crashed remotely, knocking the shared connection and dependent services offline rather than exposing data. At CVSS 8.8 the impact is rated high because a single request can take down the service, and the 22 percent EPSS score puts it meaningfully above background noise for opportunistic scanning. It has not been added to CISA's Known Exploited Vulnerabilities catalog and is not tied to ransomware campaigns.

Do this: Disable Internet Connection Sharing where it is not actually needed and patch remaining 1809 or Server 2019 hosts that require it.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2025-21212

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

I am an IT admin assessing a vulnerability. Facts for CVE-2025-21212 (source: https://senserva.com/cve/CVE-2025-21212.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-21212: Medium severity Microsoft vulnerability, CVSS 6.5
- EPSS 30-day exploitation probability: 24%
- Actively exploited (CISA KEV): no
- Fixed by: KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052105, KB5052106
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch this cycle

Not confirmed exploited yet, but the 30-day exploit probability is high (EPSS 24%).

Fixed by KB5051974 and 8 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Patch in this maintenance window; do not let it slip to the next one.

Official patch(es) for CVE-2025-21212

Elevated priority: high severity or a meaningful exploitation probability, sooner if an affected product is internet-facing. In Intune or Defender, confirm whether the fixing updates KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052105, KB5052106 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Apply the Microsoft security updates below to fix CVE-2025-21212. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.

KB5051974 KB5051979 KB5051980 KB5051987 KB5051989 KB5052000 KB5052006 KB5052105 KB5052106

Scope and sources

Affected products

Fixed by the same updates

CVE-2025-21418 CVE-2025-21391 CVE-2025-21190 CVE-2025-21200 CVE-2025-21201 CVE-2025-21208 CVE-2025-21337 CVE-2025-21368

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC FIRST.org EPSS

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