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CVE-2024-21351

From Exploited flaws, HARD’s guide to the flaws being used in attacks · Checked
This article is about a flaw in Microsoft Windows. For every flaw being used in attacks, see Exploited flaws; for Microsoft’s, see Microsoft flaws being used in attacks.

CVE-2024-21351 is a security flaw in Microsoft Windows, Microsoft’s operating system for PCs and servers. Attackers can run their own code on Microsoft Windows. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 13 Feb 2024.[1]

Microsoft Windows is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Fixed in version 10.0.10240.20469, 10.0.14393.6709, 10.0.17763.5458 and 10.0.19044.4046 and others.

Description

CISA calls it a smartScreen security feature bypass in Microsoft Windows. In its words: “Microsoft Windows SmartScreen contains a security feature bypass vulnerability that allows an attacker to bypass the SmartScreen user experience and inject code to potentially gain code execution, which could lead to some data exposure, lack of system availability, or both.”[1]

The underlying weakness is code injection (CWE-94), in MITRE’s list of common software weaknesses.[2]

It scores 7.6 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]

Affected versions

NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]

ProductFixed in
Windows 10 Version 150710.0.10240.20469
Windows 10 Version 160710.0.14393.6709
Windows 10 Version 180910.0.17763.5458
Windows 10 Version 21H210.0.19044.4046
Windows 10 Version 22H210.0.19045.4046
Windows 11 version 21H210.0.22000.2777
Windows 11 version 22H210.0.22621.3155
Windows 11 version 22H310.0.22631.3155

Every device with Microsoft Windows needs the update.

Exploitation

CISA added it to its catalog of known exploited vulnerabilities on 13 Feb 2024, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 5 Mar 2024 to fix it.[1]

FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 28%. That’s in the top 2% of the flaws it scores.[4]

CISA assesses it as not automatable: each attack takes some work.

CISA doesn’t say who was attacked, or how.

Fix

Microsoft has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]

  1. Update Microsoft Windows now.On Windows: Settings, Windows Update, Check for updates, then restart. Office updates come the same way, or from any Office app: File, Account, Update Options. Then turn on automatic updates, so the next fix arrives on its own.
  2. Check you’re on 10.0.10240.20469 or later.Fixed in version 10.0.10240.20469, 10.0.14393.6709, 10.0.17763.5458 and 10.0.19044.4046 and others. Anything older is what attackers are going after.
  3. If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.

Timeline

DateEvent
The flaw is made public in the National Vulnerability Database, with a severity score of 7.6.[2]
CISA adds it to its catalog of flaws known to be used in attacks.[1]
CISA’s deadline for US government agencies to fix it.[1]
FIRST puts the odds of it being used in attacks in the next 30 days at 28%.[4]

See also

Other Microsoft Windows flaws

Other code injection flaws

Added the same day

  • CVE-2024-21412, Microsoft Windows: internet shortcut files security feature bypass ·

Every Microsoft flaw on CISA’s list · Everything added in February 2024

References

  1. ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Windows SmartScreen Security Feature Bypass Vulnerability”. Known Exploited Vulnerabilities Catalog, added 13 Feb 2024.
  2. ^ National Institute of Standards and Technology. “CVE-2024-21351 Detail”. National Vulnerability Database, published 13 Feb 2024.
  3. ^ Microsoft. Advisories and fixes: msrc.microsoft.com, msrc.microsoft.com.
  4. ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.278, percentile 98.1, 31 Oct 2026.
  5. CVE Program. “CVE-2024-21351”. The official CVE record.

This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.