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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2021.
IpadosOperating system · Apple

CVE-2021-1879

MEDIUM · 6.1 CVSS v3.1 Published 2021-04-02
Fix available
A fix is available. Upgrade to 7.3.3 / 12.5.2 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild 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
This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. Apple is aware of a report that this issue may have been actively exploited..

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

A universal cross-site scripting (UXSS) vulnerability in WebKit caused by improper object lifecycle management. Processing maliciously crafted web content allows attackers to execute JavaScript in the context of any origin, bypassing same-origin policy protections.

MitigationApply the vendor-provided security updates (iOS 12.5.2, iOS/iPadOS 14.4.2, watchOS 7.3.3) to all affected devices. Until patched, users should avoid visiting untrusted websites.

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
IpadosOperating system
Affected:< 14.4.2
Iphone OsOperating system
Affected:< 12.5.2>= 13.0, < 14.4.2
WatchosOperating system
Affected:< 7.3.3

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
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 checks

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

  1. Identify the Apple device type
    Determine if the device is an iPhone, iPad, or Apple Watch. This matters because the affected version ranges differ slightly between iPhone/iPad and Apple Watch.
    Affected if Device is an iPhone, iPad, or Apple Watch running iOS, iPadOS, or watchOS respectively.
  2. Check iOS/iPadOS version on iPhone or iPad
    Go to Settings > General > About > Version to view the installed iOS or iPadOS version number.
    Affected if The version displayed is less than 14.4.2, or less than 12.5.2 (for iOS 12.x only devices).
  3. Check watchOS version on Apple Watch
    Open the Watch app on your paired iPhone, go to General > About, or open Settings on the Apple Watch itself and navigate to General > About > Version.
    Affected if The version displayed is less than 7.3.3.
  4. Determine if WebKit-based browser is in use
    Verify that Safari or any third-party browser (that uses WebKit) is installed and could be used to process untrusted web content. On Apple devices, all browsers use WebKit as the rendering engine.
    Affected if Safari or any WebKit-based browser is available on the device.
  5. Verify same-origin policy exposure
    Confirm that the device is used for browsing the web and could potentially visit untrusted websites. This vulnerability is triggered by processing malicious web content.
    Affected if The device is used for web browsing and could access arbitrary websites.

A user is affected if they are running iOS/iPadOS versions prior to 14.4.2 (or prior to 12.5.2 on iOS 12-only devices) or watchOS prior to 7.3.3, and they use the device for web browsing with WebKit-based browsers.

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 7.3.3 / 12.5.2 / 14.4.2 or later
Fixed in 7.3.312.5.214.4.2
Interim mitigation

Apply the vendor-provided security updates (iOS 12.5.2, iOS/iPadOS 14.4.2, watchOS 7.3.3) to all affected devices. Until patched, users should avoid visiting untrusted websites.

Recommended fix High confidence

iOS 12.5.2 (for iOS 12.x devices), iOS 14.4.2 (for iOS 13.x-14.x devices), iPadOS 14.4.2, or watchOS 7.3.3

  1. Back up your iOS device data using iCloud or iTunes before updating
  2. On iPhone or iPad: Go to Settings > General > Software Update and download/install the latest available update
  3. On Apple Watch: On your iPhone, open the Watch app, go to My Watch > General > Software Update and install the update
  4. After updating, verify the version in Settings > General > About to confirm you have iOS 12.5.2, iOS 14.4.2, iPadOS 14.4.2, or watchOS 7.3.3 or later

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

Fix this in Ipados Exploited in the wild — priority engagement
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2021-1879 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