dbcve.org
SafariWeb browser · Apple

CVE-2021-30953

HIGH · 8.8 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to 8.3 / 15.2 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
An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2 and iPadOS 15.2, watchOS 8.3. 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

A memory safety vulnerability in WebKit (Apple's browser engine) allows an out-of-bounds read when processing maliciously crafted web content. The issue was addressed with improved bounds checking and affects Safari across multiple Apple platforms (iOS, iPadOS, macOS, tvOS, watchOS). Successful exploitation can lead to arbitrary code execution.

MitigationApply the vendor patches by updating to iOS 15.2+, iPadOS 15.2+, macOS Monterey 12.1+, tvOS 15.2+, watchOS 8.3+, or Safari 15.2+. For enterprise environments, deploy updates via MDM or software distribution tools.

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:< 15.2
FedoraOperating system
Affected:= 34= 35
Debian LinuxOperating system
Affected:= 10.0= 11.0
IpadosOperating system
Affected:< 15.2
Iphone OsOperating system
Affected:< 15.2
macOSOperating system
Affected:>= 12.0.0, <= 12.1
TvosOperating system
Affected:< 15.2
WatchosOperating system
Affected:< 8.3

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
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 the browser or WebKit runtime in use
    Determine if you are running Safari on Apple devices or WebKit-based browsers (like WebKitGTK on Linux). On Apple devices, Safari is bundled with the OS.
    Affected if The system uses Safari or a WebKit-based browser to render web content.
  2. Check Safari version on macOS
    Open Safari, go to Safari > About Safari to view the version number, or run 'defaults read /Applications/Safari.app/Contents/Info CFBundleShortVersionString' in Terminal.
    Affected if The installed Safari version is earlier than 15.2.
  3. Check iOS or iPadOS version on Apple mobile devices
    Go to Settings > General > About to view the iOS/iPadOS version. Safari is bundled with the OS and cannot be updated separately.
    Affected if The iOS or iPadOS version is earlier than 15.2.
  4. Check macOS version if Safari is bundled
    Go to Apple menu > About This Mac to view the macOS version. Safari comes pre-installed with macOS.
    Affected if The macOS version is 12.0.0 through 12.1 (inclusive), which ships with a vulnerable Safari version.
  5. Check WebKit package version on Linux (Fedora/Debian)
    On Fedora, run 'dnf list installed | grep webkit'. On Debian, run 'dpkg -l | grep webkit'. For webkit2gtk-4.0 or webkit2gtk-4.1, check the specific package version.
    Affected if The system runs Fedora 34 or 35, or Debian 10.0 or 11.0, with a WebKit package installed.

You are affected if you are running Safari before version 15.2, iOS/iPadOS before 15.2, macOS 12.0-12.1, tvOS before 15.2, watchOS before 8.3, or a WebKit package on Fedora 34/35 or Debian 10.0/11.0, and you process untrusted web content with the vulnerable component enabled.

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 8.3 / 15.2 or later
Fixed in 8.315.2
Interim mitigation

Apply the vendor patches by updating to iOS 15.2+, iPadOS 15.2+, macOS Monterey 12.1+, tvOS 15.2+, watchOS 8.3+, or Safari 15.2+. For enterprise environments, deploy updates via MDM or software distribution tools.

Recommended fix High confidence

iOS 15.2, iPadOS 15.2, macOS Monterey 12.1, Safari 15.2, tvOS 15.2, watchOS 8.3

  1. For iOS devices: Upgrade to iOS 15.2 or later via Settings > General > Software Update
  2. For iPadOS devices: Upgrade to iPadOS 15.2 or later via Settings > General > Software Update
  3. For macOS Monterey: Upgrade to 12.1 or later via System Preferences > Software Update
  4. For Safari: Upgrade to Safari 15.2 or later (included with macOS 12.1 update)
  5. For tvOS devices: Upgrade to tvOS 15.2 or later via Settings > System > Software Updates
  6. For Apple Watch: Upgrade to watchOS 8.3 or later via the Watch app on iPhone
Caveat Standard OS update; review Apple's release notes for any behavior changes

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 / QA2.0 h
10.0 hours of engineering $1,780
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,848.

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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-2021-30953 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