CVE-2021-21202

Sandbox escape via extension use-after-free

Published Apr 26, 2021 · Updated Aug 3, 2024

Use after free in Google Chrome's extensions component before 90.0.4430.72 allows attackers to escape the browser sandbox. Google identifies the extensions component but has not published the freed object's identity or the operation that reuses it. Exploitation requires a user to install a crafted malicious extension, after which the flaw breaks sandbox isolation rather than merely crashing the browser.

CVSS severity8.6
High
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use after free in Google Chrome's extensions component before 90.0.4430.72 allows attackers to escape the browser sandbox. Google identifies the extensions component but has not published the freed object's identity or the operation that reuses it. Exploitation requires a user to install a crafted malicious extension, after which the flaw breaks sandbox isolation rather than merely crashing the browser.

The record

CVE
CVE-2021-21202
Published
Apr 26, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
CWE-416, T1203
Attack vector
local
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 vectorlocal
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <90.0.4430.72

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.6NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

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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