Patch tracker / CVE reference / CVE-2026-21218

CVE-2026-21218

CVE-2026-21218 is a high severity Microsoft vulnerability with a CVSS score of 7.5. 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.

High

High severity Microsoft vulnerability, CVSS 7.5. Fixed by 3 Microsoft security updates.

Senserva AI read on CVE-2026-21218Official patches for CVE-2026-21218Change historyAdmin questions

Risk summary

CVSS base
7.5
EPSS exploit probability
1.0%
Severity
High
Schedule normally
No exploitation observed: not in the CISA KEV catalog, EPSS 1%.
Fixed by KB5077862 and 2 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 July 25, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Senserva AI Opinion for CVE-2026-21218

A spoofing flaw in .NET affecting the 10.0 runtime on macOS and Windows plus .NET 8.0 on Linux, rated High Severity at CVSS 7.5. With an exploit probability of just 1 percent and no known exploitation, this is among the lowest-urgency items in the current batch. The practical risk is applications built on these runtimes accepting content whose origin claims cannot be trusted.

Do this: Roll this into your standing monthly .NET runtime update across Windows, Linux, and macOS hosts.

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

Senserva AI Opinion and rich prompt for CVE-2026-21218

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

Full tracking and change history for CVE-2026-21218

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 1.0%. CVSS 7.5 (High).

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

Official patch(es) for CVE-2026-21218

Moderate priority: schedule it in your normal patch cycle. In Intune or Defender, confirm whether the fixing updates KB5077862, KB5077863, KB5077864 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-2026-21218. 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.

KB5077862KB5077863KB5077864

Affected products

Common questions about CVE-2026-21218

Is CVE-2026-21218 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 1.0%.

What patch fixes CVE-2026-21218?

Microsoft fixed CVE-2026-21218 in KB5077862, KB5077863, KB5077864. Download from the Microsoft Update Catalog, or let Intune, Windows Update, or WSUS deliver it.

Which products are affected by CVE-2026-21218?

.NET 10.0 installed on Mac OS, .NET 10.0 installed on Windows, .NET 8.0 installed on Linux.

Can I ask my own AI about CVE-2026-21218?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2026-21218'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 twice a day (5 AM and 3 PM US Central).

Authoritative references

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

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Lexicon: the terms on this page
CVE
Common Vulnerabilities and Exposures. A unique ID for one publicly known vulnerability, such as CVE-2025-1234.
KB
Microsoft Knowledge Base article. The identifier for a specific Microsoft update.
KEV
CISA Known Exploited Vulnerabilities. CVEs confirmed exploited in the wild. Fix these first.
CVSS
Common Vulnerability Scoring System. A standardized Severity score from 0 to 10.
EPSS
Exploit Prediction Scoring System. The probability a CVE will be exploited in the next 30 days.
MSRC
Microsoft Security Response Center. Microsoft's Patch Tuesday advisories and KB-to-CVE mapping.
NVD
National Vulnerability Database (NIST). Authoritative CVE metadata and CVSS scores.
Ransomware
The vulnerability is linked to known ransomware activity.
Reference: Microsoft CVE and vulnerability management, the full CVE-to-patch lookup ranked by real-world risk, and the Microsoft patching guide, how Intune, Windows Autopatch, Defender, and Azure Update Manager fit together.
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.