CVE-2021-27085: Microsoft Internet Explorer Remote Code Execution Vulnerability

Patch now

HIGH 8.8EXPLOITEDWATCHLISTDOWNGRADE

CVE-2021-27085 is a high-severity flaw (CVSS 8.8) affecting internet explorer, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Internet Explorer Remote Code Execution Vulnerability

Why this priority

High severity
EPSS top 7%: very likely to be exploited
Exploited in the wild (CISA KEV)
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	5.4% (top 7%)
CISA exploited list	Yes, fix due 2021-11-17
Published	2021-03-11
Last modified	2026-08-19

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-08-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-03-11 16:15 UTCPublished CVE record published
2021-11-03Exploited Added to the CISA Known Exploited Vulnerabilities list
2021-11-17Deadline CISA due date for US federal agencies to patch
2026-08-19 19:22 UTCUpdated Record last modified

microsoft internet explorer DOWNGRADE

Affected: 11

Fixed in: no fixed release known

Safe to downgrade to: a release before 11

1. Check installed version

apt-cache policy internet-explorer || rpm -q internet-explorer || internet-explorer --version

2. No fixed release: DOWNGRADE to a release before 11 (Debian / Ubuntu)

apt-cache madison internet-explorer sudo apt install internet-explorer=<VERSION_BEFORE_11> sudo apt-mark hold internet-explorer

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list internet-explorer sudo dnf downgrade internet-explorer-<VERSION_BEFORE_11> sudo dnf versionlock add internet-explorer

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · bitcoin-core-selinux · FIXED · 0.3-2.fc46 · FEDORA-2026-51fc806272 · source

sudo dnf upgrade --advisory=FEDORA-2026-51fc806272

Fedora ELN · guestfs-tools · FIXED · 1.57.5-1.eln159 · FEDORA-2026-9577c5ec16 · source

sudo dnf upgrade --advisory=FEDORA-2026-9577c5ec16

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-27085?

internet explorer: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-27085 being exploited?

Yes. CVE-2021-27085 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2021-27085 affect?

CVE-2021-27085 affects internet explorer. Severity is high (CVSS 8.8). Internet Explorer Remote Code Execution Vulnerability

How urgent is CVE-2021-27085?

Priority 84/100. High severity; EPSS top 7%: very likely to be exploited; Exploited in the wild (CISA KEV); On your watchlist

Software pages

Internet Explorer vulnerabilities

Related CVEs

CVE-2015-2423 MEDIUM 4.3 DOWNGRADE DOWNGRADE Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Window
CVE-2011-3389 MEDIUM 4.3 MITIGATE MITIGATE The SSL protocol, as used in certain configurations in Microsoft Windows and Microsoft Internet Explorer, Mozi
CVE-2017-8529 MEDIUM 6.5 DOWNGRADE MITIGATE Internet Explorer in Microsoft Windows 7 SP1, Windows Server 2008 R2 SP1, Windows 8.1 and Windows RT 8.1, and
CVE-2021-26411 HIGH 8.8 EXPLOITED MITIGATE DOWNGRADE Microsoft Internet Explorer Memory Corruption Vulnerability
CVE-2000-0982 HIGH 7.5 DOWNGRADE Internet Explorer before 5.5 forwards cached user credentials for a secure web site to insecure pages on the s

References

← Back to latest CVEs