Patch tracker / CVE reference / CVE-2025-21400

CVE-2025-21400

CVE-2025-21400 is a high severity Microsoft vulnerability with a CVSS score of 8.0. Its EPSS score puts the probability of exploitation in the next 30 days at 34%. Microsoft has shipped the fix: deploy one of the 3 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

High

8.0

CVSS

34%

EPSS, 30 days

High

Severity

Not in the CISA KEV catalog. EPSS exploit probability 34%. CVSS 8.0 (High).

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

Senserva AI Opinion for CVE-2025-21400

An authenticated remote code execution flaw in SharePoint Server 2016, 2019, and Subscription Edition, High Severity at CVSS 8.0, but with a 30 percent EPSS score that is roughly ten times higher than the other SharePoint entries on this page. Elevated EPSS on a SharePoint bug is a leading indicator worth respecting given how fast prior SharePoint exploits spread once weaponized. Any phished user account can supply the required authentication.

Do this: Patch this SharePoint CVE ahead of the lower-EPSS ones and check farm audit logs for unusual authenticated requests if patching was delayed.

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

Senserva AI Opinion and rich prompt for CVE-2025-21400

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-2025-21400 (source: https://senserva.com/cve/CVE-2025-21400.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-21400: High severity Microsoft vulnerability, CVSS 8.0
- EPSS 30-day exploitation probability: 34%
- Actively exploited (CISA KEV): no
- Fixed by: KB5002678, KB5002681, KB5002685
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 34%).

Fixed by KB5002678 and 2 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-2025-21400

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 KB5002678, KB5002681, KB5002685 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-2025-21400. 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.

KB5002678 KB5002681 KB5002685

Scope and sources

Affected products

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.