How severe is CVE-2021-27085?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2021-27085 known to be exploited?

Yes. CVE-2021-27085 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.

Vulnerability in Microsoft Internet Explorer

CVE-2021-27085

Internet Explorer Remote Code Execution Vulnerability

Published 2021-03-11 · last modified 2026-08-19.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L.

EPSS exploit prediction

EPSS: 0.054 (92.6th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 92.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.054 · newest: 0.054 · change: 0.000

Affected products

Microsoft Internet Explorer — versions 11
Microsoft Internet Explorer 11 — versions 1.0.0
Microsoft Windows 10 1803
Microsoft Windows 10 1809
Microsoft Windows 10 1909
Microsoft Windows 10 2004
Microsoft Windows 10 20h2
Microsoft Windows Server 2019

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2021-11-03. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2021-11-17.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

af854a3a-2127-422b-91ae-364da2661108 (Patch, Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
msrc.microsoft.com/update-guide/vulnerability/CVE-2021-27085 (vendor-advisory, Patch, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-27085?: CVE-2021-27085 is a high-severity vulnerability in Microsoft Internet Explorer. CVSS score: 8.8/10. Published 2021-03-11.
How severe is CVE-2021-27085?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2021-27085 known to be exploited?: Yes. CVE-2021-27085 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.