CVE-2021-38021Network attack vector

Navigation restriction bypass via CSS preload referrer

Published Dec 23, 2021 · Updated Aug 4, 2024

Inappropriate referrer handling in Google Chrome before 96.0.4664.45 allows remote attackers to bypass navigation restrictions via crafted HTML. Blink's HTML parser used a document-controlled base URL, rather than the document URL, as the referrer for inline-style @import preload requests. A victim must load attacker-controlled HTML; the demonstrated effect is cross-origin stylesheet-preload referrer manipulation, not code execution.

CVSS severity6.5
Medium
EPSS probability0.79%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Inappropriate referrer handling in Google Chrome before 96.0.4664.45 allows remote attackers to bypass navigation restrictions via crafted HTML. Blink's HTML parser used a document-controlled base URL, rather than the document URL, as the referrer for inline-style @import preload requests. A victim must load attacker-controlled HTML; the demonstrated effect is cross-origin stylesheet-preload referrer manipulation, not code execution.

The record

CVE
CVE-2021-38021
Published
Dec 23, 2021
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 <96.0.4664.45

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <96.0.4664.45

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 11, 2026Sep 17, 2026
Latest reporting daySep 17, 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.

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Technologies

Your stack

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Your stack

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