dbcve.org
SafariWeb browser · Apple

CVE-2021-30934

HIGH · 8.8 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to 8.3 / 12.1 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 buffer overflow 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 buffer overflow vulnerability in WebKit (the rendering engine used by Safari and system browsers on Apple devices) allows arbitrary code execution when processing maliciously crafted web content. The issue was addressed with improved memory handling, indicating insufficient bounds checking when processing web content led to memory corruption.

MitigationApply the vendor-supplied security updates (tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS/iPadOS 15.2, watchOS 8.3 or later) to all affected devices. Prioritize internet-facing systems and devices with browser access to external 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:< 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
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. Check Safari version on macOS
    Open Safari and go to Safari > About Safari. Compare the version number to the affected range (< 15.2).
    Affected if The installed Safari version is lower than 15.2 on macOS.
  2. Check iOS or iPadOS version
    On the device, go to Settings > General > About. Note the version number. Compare to the affected range (< 15.2).
    Affected if The iOS or iPadOS version is lower than 15.2.
  3. Check watchOS version
    On the Apple Watch, open the Settings app, go to General > About, or check via the Watch app on iPhone. Compare version to < 8.3.
    Affected if The watchOS version is lower than 8.3.
  4. Check tvOS version
    Go to Settings > General > About > Version on the Apple TV. Compare to the affected range (< 15.2).
    Affected if The tvOS version is lower than 15.2.
  5. Check macOS version for WebKit exposure
    Go to System Preferences > Software Update to verify the installed macOS version. The vulnerability affects macOS 12.0 up to but not including 12.1.
    Affected if The macOS version is 12.0 or 12.0.x (Monterey).
  6. Check WebKit package version on Linux (Fedora/Debian)
    Use the system package manager to query the webkit2gtk or webkitgtk package version. For Fedora: `dnf list installed webkit2gtk4`. For Debian: `dpkg -l libwebkit2gtk-4.0-37` or similar. Compare against any available security advisories for the distribution.
    Affected if The WebKit package version is unpatched and matches the affected Fedora (34, 35) or Debian (10, 11) releases.

The environment is affected if any Apple device (Safari, iOS, iPadOS, macOS, tvOS, watchOS) or Linux system running WebKit is at a version lower than the fixed releases (Safari 15.2, iOS/iPadOS 15.2, macOS 12.1, tvOS 15.2, watchOS 8.3, or patched Fedora/Debian packages).

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 (tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS/iPadOS 15.2, watchOS 8.3 or later) to all affected devices. Prioritize internet-facing systems and devices with browser access to external content.

Recommended fix High confidence

Upgrade to iOS 15.2 / iPadOS 15.2 / watchOS 8.3 / tvOS 15.2 / macOS Monterey 12.1 / Safari 15.2; apply latest Fedora/Debian security updates

  1. For Apple devices: Upgrade to iOS 15.2 or later via Settings > General > Software Update
  2. For Apple devices: Upgrade to iPadOS 15.2 or later via Settings > General > Software Update
  3. For Apple devices: Upgrade to watchOS 8.3 or later via the Watch app on iPhone
  4. For Apple devices: Upgrade to tvOS 15.2 or later via Settings > General > Apple TV Software Update
  5. For macOS Monterey: Upgrade to 12.1 or later via System Preferences > Software Update
  6. For Safari: Upgrade to Safari 15.2 which comes with macOS Monterey 12.1 or later
  7. For Fedora systems: Run 'sudo dnf update' to apply security updates addressing this CVE
  8. For Debian systems: Run 'sudo apt update && sudo apt upgrade' to apply security updates
Caveat Standard OS upgrade considerations apply - review Apple's release notes for Monterey 12.1 and ensure compatibility with existing software

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

Fix this in Safari Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2021-30934 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