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ChromeWeb browser · Google

CVE-2021-30555

HIGH · 8.8 CVSS v3.1 Published 2021-07-02
Fix available
A fix is available. Upgrade to 91.0.4472.114 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Use after free in Sharing in Google Chrome prior to 91.0.4472.114 allowed an attacker who convinced a user to install a malicious extension to potentially exploit heap corruption via a crafted HTML page and user gesture.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Use-after-free vulnerability in Chrome's Sharing feature allows a malicious extension combined with a crafted HTML page to access freed memory, potentially leading to heap corruption. The attack requires user gesture interaction and a malicious extension to be installed.

MitigationUpdate Google Chrome to version 91.0.4472.114 or later. Review and limit browser extension permissions to prevent installation of untrusted extensions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ChromeWeb browser
Affected:< 91.0.4472.114

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if Google Chrome is installed
    Navigate to chrome://settings/help or use system commands: Windows: reg query 'HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Google Chrome', macOS: ls /Applications/ | grep Chrome, Linux: google-chrome --version or which google-chrome
    Affected if Chrome browser is present on the system
  2. Determine the installed Chrome version
    Open chrome://settings/help in Chrome browser, or run 'google-chrome --version' from command line, or check the version from the installation path found in the previous step
    Affected if The displayed version number is less than 91.0.4472.114 (e.g., 91.0.4472.101, 90.x.x.x, etc.)
  3. Review installed browser extensions
    Navigate to chrome://extensions/ and enable 'Developer mode' to see extension IDs and sources. Check for any extensions that are not from trusted developers or were installed without explicit user consent
    Affected if One or more untrusted, unknown, or malicious extensions are installed, especially those with broad permissions (e.g., read/write access to page content, tabs, or downloads)
  4. Verify Sharing feature accessibility
    The Sharing feature is built into Chrome. Access it by clicking the Share icon in the Chrome toolbar or using the context menu on a page. This is a default feature in Chrome.
    Affected if The Sharing feature is accessible and functional (this confirms the vulnerable code path exists in the installed version)

The environment is affected if Google Chrome is installed with a version below 91.0.4472.114 AND a malicious or untrusted extension is present, since the exploit requires both the vulnerable code and a malicious extension with user interaction to trigger the use-after-free.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 91.0.4472.114 or later
Fixed in 91.0.4472.114
Interim mitigation

Update Google Chrome to version 91.0.4472.114 or later. Review and limit browser extension permissions to prevent installation of untrusted extensions.

Recommended fix High confidence

Chrome 91.0.4472.114 or later

  1. 1. Open Google Chrome browser on your system
  2. 2. Click on the three-dot menu icon in the top-right corner
  3. 3. Select 'Settings' from the dropdown menu
  4. 4. In the left sidebar, click on 'About Chrome'
  5. 5. Chrome will automatically check for updates and display the current version
  6. 6. If an update is available, click 'Update Google Chrome'
  7. 7. Click 'Relaunch' to restart the browser and apply the update
  8. 8. Verify the version is 91.0.4472.114 or later by returning to About Chrome
Caveat Minor: Some older extensions or websites using deprecated APIs may require updates

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Chrome Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-30555 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data