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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.
SafariWeb browser · Apple

CVE-2021-30661

HIGH · 8.8 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 7.4 / 11.3 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
A use after free issue was addressed with improved memory management. This issue is fixed in Safari 14.1, iOS 12.5.3, iOS 14.5 and iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3. Processing maliciously crafted web content may lead to arbitrary code execution. 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 use-after-free vulnerability in WebKit (the rendering engine used by Safari and other Apple browsers) allows arbitrary code execution when processing maliciously crafted web content. The vulnerability stems from improper memory management where memory is accessed after being freed, potentially allowing an attacker to execute arbitrary code in the context of the victim's browser.

MitigationApply the vendor patches: update Safari to 14.1 or later, iOS/iPadOS to 14.5 or later, watchOS to 7.4 or later, tvOS to 14.5 or later, macOS Big Sur to 11.3 or later, or iOS 12.5.3 for older devices. For systems that cannot be updated, restrict access to untrusted web content.

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
IpadosOperating system
Affected:< 14.5
Iphone OsOperating system
Affected:< 12.5.3>= 14.0, < 14.5
macOSOperating system
Affected:>= 11.0, < 11.3
TvosOperating system
Affected:< 14.5
WatchosOperating system
Affected:< 7.4

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 the Apple platform and product
    Determine whether you use Safari on macOS, or iOS, iPadOS, watchOS, or tvOS on Apple devices. Note that this vulnerability affects WebKit across all these platforms.
    Affected if The device runs any of the affected products listed in the CVE.
  2. Check Safari version on macOS
    Open Safari, go to Safari > About Safari to view the version number. Alternatively, run 'safari-version' in Terminal or check System Preferences > Software Update.
    Affected if The installed Safari version is lower than 14.1 on macOS.
  3. Check iOS or iPadOS version
    Open Settings > General > About on the iPhone or iPad to view the iOS/iPadOS version.
    Affected if The device runs iOS/iPadOS version 14.0 to 14.4 (less than 14.5), or iOS version 12.5.2 or earlier (less than 12.5.3).
  4. Check macOS Big Sur version
    Open System Preferences > Software Update, or run 'sw_vers' in Terminal to see the macOS version number.
    Affected if macOS Big Sur (version 11.0 to 11.2) is installed, which is lower than 11.3.
  5. Check watchOS or tvOS version
    On Apple Watch, open Settings > General > About. On Apple TV, go to Settings > General > About.
    Affected if watchOS is lower than 7.4, or tvOS is lower than 14.5.

A user is affected if any of their Apple devices (Safari, iOS, iPadOS, macOS, watchOS, tvOS) run a version that falls within the specified vulnerable ranges.

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 7.4 / 11.3 / 12.5.3 or later
Fixed in 7.411.312.5.3
Interim mitigation

Apply the vendor patches: update Safari to 14.1 or later, iOS/iPadOS to 14.5 or later, watchOS to 7.4 or later, tvOS to 14.5 or later, macOS Big Sur to 11.3 or later, or iOS 12.5.3 for older devices. For systems that cannot be updated, restrict access to untrusted web content.

Recommended fix High confidence

Safari 14.1, iOS 12.5.3, iOS 14.5, iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3

  1. For iPhone users: Go to Settings > General > Software Update and install iOS 14.5 (or iOS 12.5.3 for devices that cannot run iOS 14)
  2. For iPad users: Go to Settings > General > Software Update and install iPadOS 14.5
  3. For Mac users (macOS Big Sur 11.x): Go to System Preferences > Software Update and install macOS Big Sur 11.3
  4. For Apple Watch users: Open the Watch app on iPhone, go to General > Software Update and install watchOS 7.4
  5. For Apple TV users: Go to Settings > System > Software Updates and install tvOS 14.5
  6. For Safari standalone: Update through macOS Big Sur 11.3 or download Safari 14.1 from Apple
Caveat Apple minor version upgrades typically have minimal breaking changes; however, older devices may not support the update and some legacy software may have compatibility issues

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

Fix this in Safari Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing2.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,900
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,640.

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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-2021-30661 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