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CVE-2021-33771

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

CVSS 3.17.8HighEPSS percentile96th10% chance in 30 daysCISA KEVListedsince 2021-11-03, due 2021-11-17
No public exploit knownFix5 products5 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 1507Affected: ≥ 10.0.10240.0, < 10.0.10240.19003Upgrade to: 10.0.10240.19003Affected: ≥ 10.0.14393.0, < 10.0.14393.4530Upgrade to: 10.0.14393.4530Affected: ≥ 10.0.17763.0, < 10.0.17763.2061Upgrade to: 10.0.17763.2061Affected: ≥ 10.0.0, < 10.0.18363.1679Upgrade to: 10.0.18363.1679 + 3 more branchesStated by: CVE record
  • Microsoft Windows 8.1Affected: ≥ 6.3.0, < 6.3.9600.20069Upgrade to: 6.3.9600.20069Stated by: CVE record
  • Microsoft Windows Server 2012 R2Affected: ≥ 6.3.9600.0, < 6.3.9600.20069Upgrade to: 6.3.9600.20069Stated by: CVE record
  • Microsoft Windows Server 2016Affected: ≥ 10.0.14393.0, < 10.0.14393.4530Upgrade to: 10.0.14393.4530Stated by: CVE record
  • Microsoft Windows Server 2019Affected: ≥ 10.0.17763.0, < 10.0.17763.2061Upgrade to: 10.0.17763.2061Stated by: CVE record

Versions as the sources state them. 1 more product has 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 Kernel Elevation of Privilege 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.

EPSS96th
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

10% chance of exploitation activity in the next 30 days, which ranks it in the 96th percentile of scored CVEs.

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

Lifecycle

10 events over 1854 days, from the signal feeds we watch.

  1. EPSS band change0 → moderateepss band change
  2. Patch availablerecord updated
  3. OpenVAS check added
  4. Patch availablerecord updated
  5. Added to CISA KEV
  6. Publishedweakness classified

Affected products

And 38 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 7.8 by NVD.

How it is reached

  • Attack Vector LocalRequires local access to the vulnerable system (e.g. local login, malicious file)
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required LowRequires basic user-level privileges
  • User Interaction NoneNo user interaction needed — fully automated exploitation

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

Sources

References in the record

And 2 more references. See all after sign-in

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 8.1, not every advisory. This one: actively exploited.