Patch tracker / CVE reference / CVE-2025-21377
CVE-2025-21377
CVE-2025-21377 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 15 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 24%. CVSS 6.5 (Medium).
This CVE is among the lower half of tracked Microsoft CVEs by EPSS exploit probability.
This NTLM hash disclosure flaw lets an attacker coerce affected Windows 10 1809 and Server 2019 systems into leaking authentication material that can be relayed or cracked to impersonate a user. The 8.8 CVSS score reflects how directly that leaked hash undermines Windows authentication, and a 22 percent EPSS score puts it well above a typical low-interest CVE for near-term exploitation. Neither CISA KEV nor ransomware operators have picked it up yet, but any system still running the aging 1809 build is already a weaker link in the domain.
Do this: Patch or retire remaining Windows 10 1809 and Server 2019 hosts and monitor for anomalous NTLM authentication attempts against them.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2025-21377
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Official patch(es) for CVE-2025-21377
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 KB5051972, KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052016, KB5052020, KB5052038, KB5052040, KB5052042, 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-2025-21377. 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.