Patch tracker / CVE reference / CVE-2025-21273

CVE-2025-21273

CVE-2025-21273 is a critical severity Microsoft vulnerability with a CVSS score of 9.8. Its EPSS score puts the probability of exploitation in the next 30 days at 81%. Microsoft has shipped the fix: deploy one of the 14 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Critical

Risk summary

9.8

CVSS

81%

EPSS, 30 days

Critical

Severity

Senserva AI Opinion for CVE-2025-21273

This is a critical Remote Code Execution flaw in the Windows Telephony Service affecting Windows 10 version 1809 and Windows Server 2019. With a CVSS score of 9.8 and an 81 percent EPSS exploit probability, the odds of active exploitation are unusually high even though it is not yet listed in CISA KEV. The Telephony Service being network reachable makes this a strong candidate for wormable or remote attacks against unpatched 1809 hosts.

Do this: Apply the Microsoft patch to all Windows 10 1809 and Windows Server 2019 systems now, prioritizing any hosts where the Telephony Service is running and exposed.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2025-21273

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-2025-21273 (source: https://senserva.com/cve/CVE-2025-21273.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-21273: Critical severity Microsoft vulnerability, CVSS 9.8
- EPSS 30-day exploitation probability: 81%
- Actively exploited (CISA KEV): no
- Fixed by: KB5049981, KB5049983, KB5049984, KB5049993, KB5050004, KB5050006, KB5050008, KB5050009, KB5050013, KB5050021, KB5050048, KB5050049, KB5050061, KB5050063
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 81%).

Fixed by KB5049981 and 13 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.

Full tracking and change history for CVE-2025-21273

Published

2025-01-14

Last revised

2025-01-14

Changes tracked

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Exploitation and severity

Not in the CISA KEV catalog. EPSS exploit probability 81%. CVSS 9.8 (Critical).

This CVE is among the top 25% of tracked Microsoft CVEs by EPSS exploit probability.

Official patch(es) for CVE-2025-21273

High priority: EPSS puts the odds of near-term exploitation high. In Intune or Defender, confirm whether the fixing updates KB5049981, KB5049983, KB5049984, KB5049993, KB5050004, KB5050006, KB5050008, KB5050009, KB5050013, KB5050021, KB5050048, KB5050049, KB5050061, KB5050063 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-2025-21273. 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.

KB5049981 KB5049983 KB5049984 KB5049993 KB5050004 KB5050006 KB5050008 KB5050009 KB5050013 KB5050021 KB5050048 KB5050049 KB5050061 KB5050063

Affected products

Fixed by the same updates

If you are patching CVE-2025-21273, the same updates also fix these:

CVE-2025-21333 CVE-2025-21334 CVE-2025-21335 CVE-2024-49120 CVE-2024-7344 CVE-2025-21176 CVE-2025-21189 CVE-2025-21193

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.