dbcve.org
Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 26 Mar 2026.
SafariWeb browser · Apple

CVE-2021-30952

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 →
97/100
Remediation priority · Urgent
In the wild Public exploit 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 integer overflow was addressed with improved input validation. 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

Integer overflow vulnerability in WebKit allowing arbitrary code execution via maliciously crafted web content. The fix implements improved input validation to prevent the overflow condition. This affects Safari and WebKit-based browsers on multiple Apple platforms.

MitigationApply vendor patches: update to iOS 15.2/iPadOS 15.2, macOS Monterey 12.1, Safari 15.2, tvOS 15.2, or watchOS 8.3 as appropriate for affected devices.

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 Safari version on macOS or iOS
    On macOS: open Safari, go to Safari > About Safari. On iOS/iPadOS: go to Settings > Safari > About. Note the version number displayed.
    Affected if The version is earlier than 15.2
  2. Identify the iOS/iPadOS version
    Go to Settings > General > About on the device and note the version number.
    Affected if The version is earlier than 15.2
  3. Identify the macOS version
    Click the Apple menu > About This Mac. Note the version number (for macOS Monterey, look for version 12.x).
    Affected if The macOS version is 12.0 through 12.0.x (any 12.0.x version before 12.1)
  4. Identify the tvOS or watchOS version
    On Apple TV: go to Settings > General > About > Version. On Apple Watch: open the Watch app on iPhone > General > About > Watch version.
    Affected if The tvOS version is earlier than 15.2 or the watchOS version is earlier than 8.3
  5. Check for WebKit-based browsers on Linux (Fedora/Debian)
    For Fedora: run `dnf list installed webkit2gtk4` or check installed packages for webkit. For Debian: run `dpkg -l | grep webkit` to list installed WebKit packages.
    Affected if WebKit packages from Fedora 34/35 or Debian 10.0/11.0 are installed and unpatched

You are affected if you use Safari before version 15.2, iOS/iPadOS before 15.2, macOS 12.0.x before 12.1, tvOS before 15.2, watchOS before 8.3, or unpatched WebKit packages on 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 vendor patches: update to iOS 15.2/iPadOS 15.2, macOS Monterey 12.1, Safari 15.2, tvOS 15.2, or watchOS 8.3 as appropriate for affected devices.

Recommended fix High confidence

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

  1. For iPhone/iPad: Go to Settings > General > Software Update and install iOS 15.2 or iPadOS 15.2
  2. For macOS Monterey: Go to System Preferences > Software Update and install macOS Monterey 12.1
  3. For Safari: Update to Safari 15.2 via macOS software update or system preferences
  4. For watchOS: On iPhone, open Watch app > General > Software Update and install watchOS 8.3
  5. For tvOS: Go to Settings > System > Software Updates and install tvOS 15.2

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

Fix this in Safari Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-30952 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-30952 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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