CVE-2021-30620Network attack vector

Content security policy bypass via crafted HTML

Published Sep 3, 2021 · Updated Aug 3, 2024

Insufficient policy enforcement in Blink in Microsoft Edge 93.0.961.38 and earlier allows remote attackers to bypass CSP via crafted HTML. Public Chromium and Microsoft records do not identify the Blink policy check that incorrectly accepts the crafted page. Exploitation requires a user to open attacker-controlled content; the bypass defeats the page's content restrictions, while further consequences depend on protected resources and page behavior.

CVSS severity8.8
High
EPSS probability4.13%
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 Blink in Microsoft Edge 93.0.961.38 and earlier allows remote attackers to bypass CSP via crafted HTML. Public Chromium and Microsoft records do not identify the Blink policy check that incorrectly accepts the crafted page. Exploitation requires a user to open attacker-controlled content; the bypass defeats the page's content restrictions, while further consequences depend on protected resources and page behavior.

The record

CVE
CVE-2021-30620
Published
Sep 3, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Microsoft Edge (Chromium-based)
Classifications
T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 3, 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

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Edge (Chromium-based)version=unspecified

Published CVSS scores

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

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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