ChromeWeb browser · Google
CVE-2021-21163
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 · uneditedInsufficient data validation in Reader Mode in Google Chrome on iOS prior to 89.0.4389.72 allowed a remote attacker to leak cross-origin data via a crafted HTML page and a malicious server.
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 confidenceInsufficient data validation in Google Chrome's Reader Mode on iOS allowed a remote attacker to leak cross-origin data. The vulnerability stemmed from improper validation in the Reader Mode feature, enabling a malicious server with a crafted HTML page to access data from other origins.
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
< 89.0.4389.72
FedoraOperating system
= 32= 33= 34
Debian LinuxOperating system
= 10.0CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
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 checksWork through these to decide whether this CVE applies to you.
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Identify if Google Chrome is installed on iOS or via Linux package managersOn iOS: Open Chrome app and tap the three dots > Settings > Version. On Linux: Check installed package with 'rpm -q google-chrome-stable' (Fedora/RHEL) or 'dpkg -l google-chrome-stable' (Debian)Affected if Chrome is not installed or the package cannot be found
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Determine the installed Chrome versionOn iOS: Check the version number shown in Chrome > Settings > Version. On Linux: Run 'google-chrome-stable --version' or check the package version from the package manager outputAffected if The version shown cannot be compared against 89.0.4389.72
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Compare installed version against the vulnerable rangeVerify if the installed version is less than 89.0.4389.72. For example, versions 88.x.x.x or earlier are vulnerableAffected if Installed version is less than 89.0.4389.72 (e.g., 88.0.4324.50, 87.0.4280.77, etc.)
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Determine if the Reader Mode feature has been usedReader Mode in Chrome iOS is typically accessed via the 'Aa' button in the address bar when viewing certain web pages. Check browser history or ask user if they have opened articles in Reader ModeAffected if The user has accessed Reader Mode on iOS to view web content
A user is affected if they have Google Chrome on iOS (or Linux through the listed distributions) with a version below 89.0.4389.72 and have used the Reader Mode feature to view web content.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor data89.0.4389.72
Update Google Chrome on iOS to version 89.0.4389.72 or later to obtain the patched browser. No server-side configuration changes are required.
Fix this in Chrome
Scoped from the published advisory
- Consultation1.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21163 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-21163 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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