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CVE-2021-33742

Exploited in the wild. In CISA KEV since 2021‑11‑03. Fixed versions are out.

CVSS 3.17.5HighEPSS percentile99th59% chance in 30 daysCISA KEVListedsince 2021-11-03, due 2021-11-17
No public exploit knownFix5 products9 fixed builds listed below

Published Updated Sources: CVE.org, NVD, BDU

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • Microsoft Windows 10 Version 1809Affected: ≥ 10.0.0, < 10.0.17763.1999Upgrade to: 10.0.17763.1999Affected: ≥ 10.0.0, < 10.0.18363.1621Upgrade to: 10.0.18363.1621Affected: ≥ 10.0.0, < 10.0.19043.1052Upgrade to: 10.0.19043.1052Affected: ≥ 10.0.0, < 10.0.19041.1052Upgrade to: 10.0.19041.1052 + 3 more branchesStated by: CVE record
  • Microsoft Windows Server 2016Affected: ≥ 10.0.0, < 10.0.14393.4467Upgrade to: 10.0.14393.4467Stated by: CVE record
  • Microsoft Windows Server 2019Affected: ≥ 10.0.0, < 10.0.17763.1999Upgrade to: 10.0.17763.1999Stated by: CVE record
  • Microsoft Windows 7Affected: ≥ 6.1.0, < 6.1.7601.25632Upgrade to: 6.1.7601.25632Affected: ≥ 6.1.0, < publicationUpgrade to: publicationStated by: CVE record
  • Microsoft Windows 8.1Affected: ≥ 6.3.0, < 6.3.9600.20045Upgrade to: 6.3.9600.20045Affected: ≥ 6.3.0, < 1.0.0.0Upgrade to: 1.0.0.0Stated by: CVE record

Versions as the sources state them. 4 more products have version data. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

Coverage timeline

0 publishers

  1. Added to CISA KEV catalog

    ·CISA KEV

Sourced from public security reporting — each date is when it was published, not when it happened.

What it is

From the CVE record

Windows MSHTML Platform Remote Code Execution Vulnerability

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS99th
CISA KEV
CISA KEV

Listed as exploited in the wild since 2021-11-03.

US federal agencies must remediate by 2021-11-17.

Apply updates per vendor instructions.
Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

59% chance of exploitation activity in the next 30 days, which ranks it in the 99th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

7 events over 1843 days, from the signal feeds we watch.

  1. OpenVAS check added
  2. Patch availablerecord updated
  3. Added to CISA KEV
  4. Publishedweakness classified, att&ck mapped

Affected products

And 39 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Scored 7.5 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction RequiredA user must click a link, open a file, or perform some action

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity HighTotal loss of integrity — attacker can modify any data in the component
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

Watch the software you run.

My Stack ranks new CVEs for your products by real-world exploitation, so the next exploited one reaches you without reading every advisory.

We'll flag the next CVE, public exploit or patch for Windows 7 Service Pack 1, not every advisory. This one: actively exploited.