Patch tracker / CVE reference / CVE-2026-21527

CVE-2026-21527

CVE-2026-21527 is a medium severity Microsoft vulnerability with a CVSS score of 6.5. Microsoft has shipped the fix: deploy one of the 4 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Medium

Medium severity Microsoft vulnerability, CVSS 6.5. Fixed by 4 Microsoft security updates.

Senserva AI read on CVE-2026-21527Official patches for CVE-2026-21527Change historyAdmin questions

Risk summary

CVSS base
6.5
EPSS exploit probability
7.7%
Severity
Medium

Senserva AI Opinion for CVE-2026-21527

CVE-2026-21527 is a spoofing flaw in on-premises Microsoft Exchange Server, hitting Subscription Edition RTM, 2016 Cumulative Update 23, and 2019 Cumulative Update 15. Spoofing on a mail server typically enables forged sender identities or manipulated content that helps phishing bypass user trust, and self-hosted Exchange remains a high-value target. Severity is Medium with a CVSS score of 6.5, there is no confirmed exploitation in CISA KEV, and EPSS estimates an 8 percent exploit probability.

Do this: Apply the latest Microsoft security update for your Exchange build (Subscription Edition RTM, 2016 CU23, or 2019 CU15) during your next patch window.

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

Senserva AI Opinion and rich prompt for CVE-2026-21527

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

Schedule normally
No exploitation observed: not in the CISA KEV catalog, EPSS 8%.
Fixed by KB5074992 and 3 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.
Do this now: Deploy with your normal update cycle. This page refreshes daily; the verdict changes the day the data does.

Updated August 7, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2026-21527

Published
2026-02-10
Last revised
2026-02-10
Changes tracked
1

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 7.7%. CVSS 6.5 (Medium).

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

Official patch(es) for CVE-2026-21527

Lower priority: patch in your normal cycle. In Intune or Defender, confirm whether the fixing updates KB5074992, KB5074993, KB5074994, KB5074995 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-2026-21527. 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.

KB5074992KB5074993KB5074994KB5074995

Affected products

Authoritative references

Official CVE record (cve.org)NVD detailMicrosoft MSRCFIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
Data notice: this page, the feeds, and the API are provided as is, for informational purposes only, without warranty of any kind. Senserva, LLC does not guarantee the accuracy, completeness, or timeliness of third-party data (MSRC, NVD, CISA KEV, EPSS) and accepts no liability for actions taken based on it; verify against the authoritative vendor advisory before acting. Built daily with Senserva Trustworthy AI. All use of this data is subject to the Senserva EULA.