CVE-2021-38016Network attack vector

Same-origin policy bypass via Background Fetch

Published Dec 23, 2021 · Updated Aug 4, 2024

Insufficient policy enforcement in Google Chrome before 96.0.4664.45 allows remote attackers to bypass the same-origin policy via crafted HTML. Google identifies the affected locus as Background Fetch but has not published which policy check is missing or how a cross-origin fetch is accepted. Exploitation requires a user to open attacker-controlled HTML; the disclosed consequence is limited to bypassing origin isolation.

CVSS severity8.8
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient policy enforcement in Google Chrome before 96.0.4664.45 allows remote attackers to bypass the same-origin policy via crafted HTML. Google identifies the affected locus as Background Fetch but has not published which policy check is missing or how a cross-origin fetch is accepted. Exploitation requires a user to open attacker-controlled HTML; the disclosed consequence is limited to bypassing origin isolation.

The record

CVE
CVE-2021-38016
Published
Dec 23, 2021
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
CWE-863, 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

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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-863Incorrect Authorization
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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