CVE-2021-21187Network attack vector

Domain spoofing via insufficient URL validation

Published Mar 9, 2021 · Updated Aug 3, 2024

Insufficient URL validation in Google Chrome before 89.0.4389.72 allows remote attackers to spoof domains through crafted IDN homographs. The URL-formatting component insufficiently validates an internationalized domain name before presenting a visually confusable domain identity. A user must open the crafted domain; the resulting visual deception can misrepresent site identity but does not itself execute code.

CVSS severity4.3
Medium
EPSS probability1.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient URL validation in Google Chrome before 89.0.4389.72 allows remote attackers to spoof domains through crafted IDN homographs. The URL-formatting component insufficiently validates an internationalized domain name before presenting a visually confusable domain identity. A user must open the crafted domain; the resulting visual deception can misrepresent site identity but does not itself execute code.

The record

CVE
CVE-2021-21187
Published
Mar 9, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <89.0.4389.72

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <89.0.4389.72

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1566.002Phishing: Spearphishing Link

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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