Patch tracker / CVE reference / CVE-2025-21217
CVE-2025-21217
CVE-2025-21217 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 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.
Risk summary
Not in the CISA KEV catalog. EPSS exploit probability 81%. CVSS 6.5 (Medium).
This CVE is among the top 10% of tracked Microsoft CVEs by EPSS exploit probability.
Windows NTLM itself is the target this time, with a spoofing weakness rated Critical 9.8 on Windows 10 1809 and Server 2019 that could let an attacker impersonate a legitimate party during authentication. The 81 percent EPSS score is among the highest in this set, meaning the exploit prediction model sees this as a strong candidate for real-world attacks even though CISA has not confirmed exploitation and there is no ransomware link yet. NTLM weaknesses are a perennial favorite for credential relay attacks, so this one deserves attention beyond its numeric score.
Do this: Patch affected hosts and confirm NTLM relay mitigations, such as SMB signing and Extended Protection for Authentication, are enabled where NTLM is still in use.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2025-21217
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Official patch(es) for CVE-2025-21217
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-2025-21217. 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.
Scope and sources
- Affected products
- Fixed by the same updates
- Authoritative references
Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.