CVE-2021-1826
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 · uneditedA logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.3, iOS 14.5 and iPadOS 14.5, watchOS 7.4, tvOS 14.5. Processing maliciously crafted web content may lead to universal cross site scripting.
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 confidenceA logic issue in WebKit allows processing of maliciously crafted web content to lead to universal cross-site scripting (UXSS), enabling an attacker to execute scripts in the context of any website regardless of origin.
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< 14.5< 14.5>= 11.0, < 11.3< 14.5< 7.4CVSS 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
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 your Apple device operating systemDetermine whether your device runs iOS, iPadOS, macOS, tvOS, or watchOS. This is necessary because each OS has different affected version ranges.Affected if The device runs any Apple operating system (iOS, iPadOS, macOS, tvOS, or watchOS)
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Check the installed OS version numberOn iOS/iPadOS: go to Settings > General > About > Version. On macOS: click Apple menu > About This Mac. On tvOS/watchOS: go to Settings > General > About. Note the version number displayed.Affected if You obtain a specific version number to compare against affected ranges
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Compare your version to the affected rangesMatch your installed version to these ranges: iOS < 14.5, iPadOS < 14.5, macOS >= 11.0 and < 11.3, tvOS < 14.5, watchOS < 7.4Affected if Your installed version falls within: iOS/iPadOS < 14.5, macOS 11.0 through 11.2.x, tvOS < 14.5, or watchOS < 7.4
You are affected if your device runs an Apple OS version lower than 14.5 for iOS/iPadOS/tvOS/watchOS, or between 11.0 and 11.3 for macOS, because the WebKit vulnerability enabling universal cross-site scripting is present in those versions.
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.
dbcve · scoped7.411.314.5
Update affected devices to macOS Big Sur 11.3, iOS/iPadOS 14.5, watchOS 7.4, or tvOS 14.5 and later to apply the vendor patch.
iOS 14.5 / iPadOS 14.5 / macOS Big Sur 11.3 / watchOS 7.4 / tvOS 14.5
- For iPhone users: Go to Settings > General > Software Update and install iOS 14.5 or later
- For iPad users: Go to Settings > General > Software Update and install iPadOS 14.5 or later
- For Mac users: Go to System Preferences > Software Update and install macOS Big Sur 11.3 or later
- For Apple Watch users: Open the Watch app on iPhone, go to General > Software Update and install watchOS 7.4 or later
- For Apple TV users: Go to Settings > System > Software Updates and install tvOS 14.5 or later
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,848.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1826 — 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-2021-1826 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