dbcve.org
SafariWeb browser · Apple

CVE-2021-30734

HIGH · 8.8 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 7.5 / 11.4 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
Multiple memory corruption issues were addressed with improved memory handling. This issue is fixed in tvOS 14.6, iOS 14.6 and iPadOS 14.6, Safari 14.1.1, macOS Big Sur 11.4, watchOS 7.5. Processing maliciously crafted web content may lead to arbitrary code execution.

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

Memory corruption vulnerability in WebKit allowing arbitrary code execution through malicious web content, affecting Safari and WebKit-based browsers on Apple devices running iOS 14.6, tvOS 14.6, watchOS 7.5, and macOS Big Sur 11.4 or earlier.

MitigationApply vendor security updates (iOS 14.6, tvOS 14.6, watchOS 7.5, macOS Big Sur 11.4, Safari 14.1.1 or later) to all affected devices to address the memory handling issues.

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
SafariWeb browser
Affected:< 14.1.1
IpadosOperating system
Affected:< 14.6
Iphone OsOperating system
Affected:< 14.6
macOSOperating system
Affected:>= 11.0.1, < 11.4
TvosOperating system
Affected:< 14.6
WatchosOperating system
Affected:< 7.5

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 macOS version on Mac computers
    Open System Preferences > About or run 'sw_vers' in Terminal. Look for the macOS version number (e.g., 11.3, 11.4, 11.5)
    Affected if macOS version is 11.0.1 through 11.3.x (any version >= 11.0.1 but < 11.4)
  2. Check iOS version on iPhone and iPad
    Go to Settings > General > About on the device. Note the iOS version number
    Affected if iOS version is any version < 14.6 (including 14.5, 14.4, etc.)
  3. Check tvOS version on Apple TV
    Go to Settings > General > About > Version on Apple TV
    Affected if tvOS version is any version < 14.6
  4. Check watchOS version on Apple Watch
    Open the Watch app on iPhone, go to General > About, or check directly on Apple Watch in Settings > General > About
    Affected if watchOS version is any version < 7.5
  5. Check Safari version
    Open Safari, go to Safari > About Safari (macOS) or Settings > Safari > About (iOS/iPadOS). Compare the Safari version to 14.1.1
    Affected if Safari version is any version < 14.1.1
  6. Verify WebKit-based browser usage
    Confirm use of Safari or any WebKit-based browser (e.g., Chrome on iOS, third-party browsers). This vulnerability is triggered through malicious web content loaded in WebKit
    Affected if Any WebKit-based browser is running on an affected OS version

You are affected if your device runs any of the listed Apple operating systems or Safari versions below the fixed versions, and you use Safari or another WebKit-based browser to browse the web.

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 7.5 / 11.4 / 14.1.1 or later
Fixed in 7.511.414.1.1
Interim mitigation

Apply vendor security updates (iOS 14.6, tvOS 14.6, watchOS 7.5, macOS Big Sur 11.4, Safari 14.1.1 or later) to all affected devices to address the memory handling issues.

Recommended fix High confidence

iOS 14.6+/iPadOS 14.6+/macOS Big Sur 11.4+/watchOS 7.5+/tvOS 14.6+/Safari 14.1.1

  1. Identify the affected Apple device/product (iPhone, iPad, Mac, Apple Watch, Apple TV, or Safari browser)
  2. Check the current installed version of the operating system or Safari
  3. For iPhone/iPad: Go to Settings > General > Software Update and upgrade to iOS/iPadOS 14.6 or later
  4. For Mac: Go to System Preferences > Software Update and upgrade to macOS Big Sur 11.4 or later
  5. For Apple Watch: Go to Settings > General > Software Update and upgrade to watchOS 7.5 or later
  6. For Apple TV: Go to Settings > System > Software Updates and upgrade to tvOS 14.6 or later
  7. For Safari on macOS: Update macOS to Big Sur 11.4 or later, which includes Safari 14.1.1
  8. After upgrading, verify the new version is installed
Caveat Standard OS upgrade considerations apply (app compatibility, data backup recommended before updating)

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

Fix this in Safari 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.

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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-2021-30734 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