CVE-2021-21205Network attack vector

Navigation restriction bypass via misclassified redirect reload

Published Apr 26, 2021 · Updated Aug 3, 2024

Insufficient navigation policy enforcement in Google Chrome on iOS before 90.0.4430.72 allows remote attackers to bypass restrictions via HTML. During a server-side 30x redirect on a user reload, the iOS navigation handler misclassifies the redirect as a reload and permits an unsafe data URL to render. A victim must load the crafted page and reload it; exploitation permits content and address-bar spoofing without interrupting the browser service.

CVSS severity8.1
High
EPSS probability1.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient navigation policy enforcement in Google Chrome on iOS before 90.0.4430.72 allows remote attackers to bypass restrictions via HTML. During a server-side 30x redirect on a user reload, the iOS navigation handler misclassifies the redirect as a reload and permits an unsafe data URL to render. A victim must load the crafted page and reload it; exploitation permits content and address-bar spoofing without interrupting the browser service.

The record

CVE
CVE-2021-21205
Published
Apr 26, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 26, 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 <90.0.4430.72

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <90.0.4430.72

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
5.8NIST NVDAV:N/AC:M/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

T1189Drive-by Compromise

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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