dbcve.org
IpadosOperating system · Apple

CVE-2021-30855

MEDIUM · 5.5 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to 8.0 / 10.15.7 or later.
See remediation →
58/100
Remediation priority · Elevated
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 validation issue existed in the handling of symlinks. This issue was addressed with improved validation of symlinks. This issue is fixed in Security Update 2021-005 Catalina, iOS 14.8 and iPadOS 14.8, iOS 15 and iPadOS 15, watchOS 8, macOS Big Sur 11.6. An application may be able to access restricted files.

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 · moderate confidence

A validation issue existed in the handling of symlinks in multiple Apple operating systems (macOS, iOS, iPadOS, and watchOS). The improper validation allowed an application to traverse symlinks and access restricted files outside the intended directory boundaries, potentially bypassing sandbox restrictions.

MitigationApply the appropriate Apple security update for the affected product: Security Update 2021-005 for macOS Catalina, iOS 14.8/iPadOS 14.8, iOS 15/iPadOS 15, watchOS 8, or macOS Big Sur 11.6.

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
IpadosOperating system
Affected:< 14.8
Iphone OsOperating system
Affected:< 14.8
Mac Os XOperating system
Affected:< 10.15.7= 10.15.7
macOSOperating system
Affected:< 11.6
TvosOperating system
Affected:< 15.0
WatchosOperating system
Affected:< 8.0

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
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

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 operating system
    Run 'sw_vers' on macOS, or check Settings > General > About on iOS/iPadOS/watchOS/tvOS to determine the product name and exact version number
    Affected if The device runs any of: iPadOS, iPhone OS, macOS, tvOS, or watchOS - proceed to version check
  2. Check macOS version
    Run 'sw_vers -productVersion' or 'system_profiler SPSoftwareDataType' to get the exact macOS build version
    Affected if Version is 10.15.7 (any build) OR less than 10.15.7 OR less than 11.6 (for macOS Big Sur)
  3. Check iOS/iPadOS version
    Check Settings > General > About > Version on the device, or use Xcode or device management tools to query the iOS version
    Affected if Version is less than 14.8
  4. Check watchOS version
    Check the Watch app on paired iPhone > My Watch > General > About, or check directly on the watch in Settings > General > About
    Affected if Version is less than 8.0
  5. Check tvOS version
    Check Settings > General > About > Version on Apple TV, or use Apple Configurator or device management tools
    Affected if Version is less than 15.0

You are affected if your device runs any of: iPadOS/iOS < 14.8, macOS 10.15.7 (any build) or < 10.15.7, macOS < 11.6, watchOS < 8.0, or tvOS < 15.0 - the symlink validation flaw exists in these unpatched versions.

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 8.0 / 10.15.7 / 11.6 or later
Fixed in 8.010.15.711.6
Interim mitigation

Apply the appropriate Apple security update for the affected product: Security Update 2021-005 for macOS Catalina, iOS 14.8/iPadOS 14.8, iOS 15/iPadOS 15, watchOS 8, or macOS Big Sur 11.6.

Recommended fix High confidence

iOS/iPadOS 14.8 or later (or iOS 15+); macOS 11.6 or Security Update 2021-005 for Catalina 10.15.7; watchOS 8.0+; tvOS 15.0+

  1. 1. Identify the Apple device type (iPhone, iPad, Mac, Apple Watch, Apple TV)
  2. 2. Check the current installed OS version in Settings > General > About (iOS/iPadOS) or System Preferences > About (macOS)
  3. 3. For iPhone/iPad: Navigate to Settings > General > Software Update and upgrade to iOS/iPadOS 14.8 or later (iOS 15+ also contains the fix)
  4. 4. For Mac: Open System Preferences > Software Update and install Security Update 2021-005 Catalina, or upgrade to macOS Big Sur 11.6 or later
  5. 5. For Apple Watch: Install watchOS 8 via the Watch app on iPhone
  6. 6. For Apple TV: Install tvOS 15 via Settings > System > Software Updates
  7. 7. After updating, verify the OS version meets or exceeds the fixed versions: iOS/iPadOS 14.8+, macOS 11.6+, watchOS 8.0+, tvOS 15.0+
Caveat iOS 15 introduced some UI and feature changes from iOS 14; minor compatibility issues possible with older apps

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

Fix this in Ipados Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing2.0 h
  • Review / QA1.0 h
12.0 hours of engineering $2,160
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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-2021-30855 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