CVE-2021-30539Network attack vector

Content Security Policy bypass via crafted HTML

Published Jun 7, 2021 · Updated Aug 3, 2024

Incorrect CSP enforcement in Google Chrome before 91.0.4472.77 allows remote attackers to bypass page security policy via crafted HTML. Public records identify the Content Security Policy implementation but do not disclose the affected code path or the incorrect operation on attacker-controlled markup. Exploitation requires a user to load the crafted page, after which prohibited content can be loaded or executed within the page security context.

CVSS severity5.4
Medium
EPSS probability1.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect CSP enforcement in Google Chrome before 91.0.4472.77 allows remote attackers to bypass page security policy via crafted HTML. Public records identify the Content Security Policy implementation but do not disclose the affected code path or the incorrect operation on attacker-controlled markup. Exploitation requires a user to load the crafted page, after which prohibited content can be loaded or executed within the page security context.

The record

CVE
CVE-2021-30539
Published
Jun 7, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
CWE-863, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 7, 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 <91.0.4472.77

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <91.0.4472.77

Published CVSS scores

5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/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.

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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