Patch tracker / CVE reference / CVE-2025-21309
CVE-2025-21309
CVE-2025-21309 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 7 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.
Critical severity Microsoft vulnerability, CVSS 9.8. Fixed by 7 Microsoft security updates.
Risk summary
Updated July 24, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2025-21309
The twin of CVE-2025-21297: a Critical CVSS 9.8 remote code execution vulnerability in Remote Desktop Services on Server 2019 and 2022, also carrying an 81 percent EPSS score. When two Critical unauthenticated-profile bugs land in RDP infrastructure simultaneously, exploit developers get two chances at the same target and defenders get one patch window to close both. Internet-exposed RDP endpoints carry nearly all of the practical risk.
Do this: Close both CVEs in one emergency window on all RDP-reachable Server 2019 and 2022 hosts, and put any internet-facing RDP behind a gateway or VPN permanently.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2025-21309
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2025-21309
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-2025-21309
High priority: EPSS puts the odds of near-term exploitation high. In Intune or Defender, confirm whether the fixing updates KB5049983, KB5049984, KB5049993, KB5050004, KB5050008, KB5050009, KB5050048 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-2025-21309. 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.
Affected products
Common questions about CVE-2025-21309
Is CVE-2025-21309 actively exploited?
It is not currently listed in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score puts the probability of exploitation in the next 30 days at 81%.
What patch fixes CVE-2025-21309?
Microsoft fixed CVE-2025-21309 in KB5049983, KB5049984, KB5049993, KB5050004, KB5050008, KB5050009, KB5050048. Download from the Microsoft Update Catalog, or let Intune, Windows Update, or WSUS deliver it.
Which products are affected by CVE-2025-21309?
Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows Server 2019.
Can I ask my own AI about CVE-2025-21309?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2025-21309's key facts: severity, CVSS, EPSS exploit probability, CISA KEV status, and the fixing KB. Copy it into Claude, ChatGPT, or Copilot for a triage plan; the data is refreshed three times a day (5 AM, 12:30 PM, and 7 PM US Central).
Fixed by the same updates
If you are patching CVE-2025-21309, the same updates also fix these:
Authoritative references
Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.
