dbcve.org
SafariWeb browser · Apple

CVE-2021-30954

HIGH · 7.8 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to 8.3 / 12.1 or later.
See remediation →
81/100
Remediation priority · High
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 type confusion issue was addressed with improved memory handling. 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 type confusion vulnerability in WebKit allows processing of maliciously crafted web content to lead to arbitrary code execution. The issue stems from improper memory handling when processing objects of unexpected types, which can be exploited to corrupt memory and achieve code execution in the context of the renderer process.

MitigationApply the vendor-supplied security updates: iOS 15.2 and later, iPadOS 15.2 and later, macOS Monterey 12.1 and later, Safari 15.2 and later, tvOS 15.2 and later, and watchOS 8.3 and later.

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, < 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
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/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 WebKit-based product in use
    Determine if the system runs Safari on macOS/iOS/iPadOS, or a WebKit-based browser on Linux (such as browsers using webkit2gtk)
    Affected if The product is Safari or any browser using the vulnerable WebKit rendering engine
  2. Check Safari version on macOS
    Open Safari, go to Safari > About Safari to view the version number
    Affected if The version is earlier than 15.2 (for macOS Big Sur and earlier) or earlier than 16.0 on newer systems
  3. Check iOS or iPadOS version
    Go to Settings > General > About on the iPhone or iPad to view the iOS version
    Affected if The version is earlier than 15.2
  4. Check macOS version
    Go to Apple menu > About This Mac to view the macOS version number
    Affected if The version is 12.0 (Monterey) through 12.0.1 through 12.0.x (any version before 12.1)
  5. Check WebKit package version on Linux
    Use the system package manager to query the webkit2gtk package version (e.g., dnf info webkit2gtk or apt show libwebkit2gtk-4.0-37)
    Affected if The installed WebKit package version corresponds to a build that predates the security fix (vendor advisories for Fedora 34, 35 and Debian 10, 11 reference this CVE)
  6. Confirm WebKit is actively used
    Verify that the identified browser or application has JavaScript enabled and processes web content
    Affected if JavaScript and web content processing are enabled in the browser settings

The environment is affected if the identified Apple product version is below the fixed release (iOS/iPadOS/tvOS/watchOS < 15.2, macOS 12.0-12.0.x, Safari < 15.2) or if the Linux WebKit package version matches the unpatched versions in Fedora 34/35 or Debian 10/11.

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 / 12.1 / 15.2 or later
Fixed in 8.312.115.2
Interim mitigation

Apply the vendor-supplied security updates: iOS 15.2 and later, iPadOS 15.2 and later, macOS Monterey 12.1 and later, Safari 15.2 and later, tvOS 15.2 and later, and watchOS 8.3 and later.

Recommended fix High confidence

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

  1. For iPhone/iPad: Go to Settings > General > Software Update and install iOS/iPadOS 15.2 or later
  2. For macOS Monterey: Go to System Preferences > Software Update and install macOS Monterey 12.1 or later
  3. For Apple Watch: Go to Settings > General > Software Update on the watch and install watchOS 8.3 or later
  4. For Apple TV: Go to Settings > System > Software Updates and install tvOS 15.2 or later
  5. For Safari: Update to Safari 15.2 via macOS update (macOS Monterey 12.1 includes Safari 15.2)
Caveat Users should back up devices before updating. Some older devices may not support these OS versions.

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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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-2021-30954 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