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SafariOperating system · Apple

CVE-2021-1788

HIGH · 8.8 CVSS v3.1 Published 2021-04-02
Fix available
A fix is available. Upgrade to 10.14.6 / 10.15.7 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
A use after free issue was addressed with improved memory management. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, tvOS 14.4, watchOS 7.3, iOS 14.4 and iPadOS 14.4, Safari 14.0.3. 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

This is a use-after-free vulnerability in WebKit (Apple's browser engine) affecting multiple Apple operating systems. When processing maliciously crafted web content, the browser may free memory while still holding a pointer to it, potentially allowing an attacker to execute arbitrary code by exploiting the dangling pointer.

MitigationApply the relevant security updates: iOS 14.4/iPadOS 14.4 for mobile devices, macOS Big Sur 11.2 or Security Update 2021-001 for Catalina/Mojave, tvOS 14.4, watchOS 7.3, or Safari 14.0.3 depending on the affected platform.

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
SafariOperating system
Affected:< 14.0.3
Debian LinuxOperating system
Affected:= 10.0
FedoraOperating system
Affected:= 33
IpadosOperating system
Affected:< 14.4
Iphone OsOperating system
Affected:< 14.4
Mac Os XOperating system
Affected:>= 10.14, < 10.14.6>= 10.15, < 10.15.7= 10.14.6= 10.15.7
macOSOperating system
Affected:>= 11.0, < 11.2
TvosOperating system
Affected:< 14.4

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. Identify your operating system
    Determine if the system is running macOS, iOS, iPadOS, tvOS, Debian Linux, or Fedora. On Apple devices, go to Settings > General > About (iOS/iPadOS/tvOS) or Apple menu > About This Mac (macOS). On Linux, run 'uname -a' or check /etc/os-release.
    Affected if The OS is any of the affected platforms listed in the CVE (Safari < 14.0.3, iOS/iPadOS < 14.4, macOS < 11.2 or specific Catalina/Mojave versions, tvOS < 14.4, Debian 10, Fedora 33)
  2. Check Safari version on macOS
    Open Safari and go to Safari > About Safari. Note the version number displayed.
    Affected if Safari version is earlier than 14.0.3 on macOS or macOS X
  3. Check iOS or iPadOS version
    Open Settings > General > About and note the version number.
    Affected if iOS or iPadOS version is earlier than 14.4
  4. Check macOS version
    Open Apple menu > About This Mac. The version is displayed (e.g., 10.15.7, 11.1, 11.2).
    Affected if macOS version is 10.14.x (before 10.14.6), 10.15.x (before 10.15.7), or 11.0-11.1 (before 11.2)
  5. Confirm WebKit usage
    Identify if any application uses WebKit for rendering web content. On Apple platforms, Safari and many third-party browsers use WebKit. Check the browser or app info to confirm the rendering engine.
    Affected if A WebKit-based browser or application is in use on an affected OS version, as the vulnerability triggers when processing malicious web content

You are affected if your Safari version is below 14.0.3, or your iOS/iPadOS/tvOS is below 14.4, or your macOS falls within the vulnerable range (10.14.x before 10.14.6, 10.15.x before 10.15.7, or 11.0-11.1), and you use WebKit 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 10.14.6 / 10.15.7 / 11.2 or later
Fixed in 10.14.610.15.711.2
Interim mitigation

Apply the relevant security updates: iOS 14.4/iPadOS 14.4 for mobile devices, macOS Big Sur 11.2 or Security Update 2021-001 for Catalina/Mojave, tvOS 14.4, watchOS 7.3, or Safari 14.0.3 depending on the affected platform.

Recommended fix High confidence

macOS 11.2+, Security Update 2021-001 for Catalina/Mojave, iOS/iPadOS 14.4+, tvOS 14.4+, Safari 14.0.3

  1. For macOS Big Sur (11.x): Update to macOS 11.2 or later via System Preferences > Software Update
  2. For macOS Catalina (10.15): Apply Security Update 2021-001 via System Preferences > Software Update
  3. For macOS Mojave (10.14): Apply Security Update 2021-001 via System Preferences > Software Update
  4. For iPhone/iPad: Update to iOS/iPadOS 14.4 or later via Settings > General > Software Update
  5. For tvOS: Update to tvOS 14.4 or later via Settings > System > Software Update
  6. For Safari: Update Safari by installing the corresponding macOS/iOS/iPadOS update (Safari 14.0.3 is included in the above updates)

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
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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-2021-1788 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