CVE-2021-43221Network attack vector

Remote code execution via undisclosed browser flaw

Published Nov 24, 2021 · Updated Aug 19, 2026

Remote code execution in Microsoft Edge (Chromium-based) before 96.0.1054.29 allows remote attackers to execute code via crafted web content. Microsoft has not published the affected browser component or the operation that mishandles the crafted content. User interaction is required, and successful exploitation runs attacker-controlled code within the browser's security context.

CVSS severity4.2
Medium
EPSS probability1.08%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Microsoft Edge (Chromium-based) before 96.0.1054.29 allows remote attackers to execute code via crafted web content. Microsoft has not published the affected browser component or the operation that mishandles the crafted content. User interaction is required, and successful exploitation runs attacker-controlled code within the browser's security context.

The record

CVE
CVE-2021-43221
Published
Nov 24, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Microsoft Edge (Chromium-based)
Classifications
CWE-94, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.0.0.0 <96.0 1954.29

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Edge (Chromium-based)version=1.0.0.0 <96.0 1954.29

Published CVSS scores

4.2MicrosoftCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.2NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0NIST NVDAV:N/AC:H/Au:N/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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