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Iphone OsOperating system · Apple

CVE-2021-30776

MEDIUM · 5.5 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 7.6 / 11.5 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 logic issue was addressed with improved validation. This issue is fixed in iOS 14.7, macOS Big Sur 11.5, watchOS 7.6, tvOS 14.7, Security Update 2021-004 Catalina. Playing a malicious audio file may lead to an unexpected application termination.

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 logic validation issue in Apple's audio file handling across iOS, macOS, watchOS, and tvOS allows a maliciously crafted audio file to trigger unexpected application termination (denial of service). The vulnerability stems from insufficient validation logic when processing audio files.

MitigationApply the vendor-supplied updates: iOS 14.7+, macOS Big Sur 11.5+, watchOS 7.6+, tvOS 14.7+, or Security Update 2021-004 for Catalina. For custom applications handling audio, implement robust input validation and error handling for audio file parsing.

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
Iphone OsOperating system
Affected:< 14.7
Mac Os XOperating system
Affected:>= 10.15, <= 10.15.6= 10.15.7
macOSOperating system
Affected:< 11.5
TvosOperating system
Affected:< 14.7
WatchosOperating system
Affected:< 7.6

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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 iOS version on iPhone or iPad
    Go to Settings > General > About > Version, or run 'sw_vers' via terminal on a Mac with the device connected, or check via Apple Configurator or Finder
    Affected if Version is lower than 14.7 (e.g., 14.6, 14.5, etc.)
  2. Check macOS version on Mac computers
    Go to Apple menu > About This Mac > Version, or run 'sw_vers' in Terminal
    Affected if Running macOS Catalina (10.15.x) at versions 10.15 through 10.15.6, or exactly 10.15.7, OR running macOS Big Sur earlier than 11.5
  3. Check watchOS version on Apple Watch
    Open the Watch app on iPhone > General > About > Version, or check via Settings on the Watch itself
    Affected if Version is lower than 7.6
  4. Check tvOS version on Apple TV
    Go to Settings > General > About > Version
    Affected if Version is lower than 14.7
  5. Determine if device processes audio files
    Verify if any applications on the device can open or play audio files (music players, media apps, messaging apps with audio attachments, voice recorders)
    Affected if The device can process audio files - this is the default behavior for most Apple devices

You are affected if your device runs any of the listed Apple OS versions lower than the fixed releases and can process audio files, which is standard functionality.

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 7.6 / 11.5 / 14.7 or later
Fixed in 7.611.514.7
Interim mitigation

Apply the vendor-supplied updates: iOS 14.7+, macOS Big Sur 11.5+, watchOS 7.6+, tvOS 14.7+, or Security Update 2021-004 for Catalina. For custom applications handling audio, implement robust input validation and error handling for audio file parsing.

Recommended fix High confidence

iOS 14.7, macOS Big Sur 11.5, watchOS 7.6, tvOS 14.7, Security Update 2021-004 Catalina

  1. Back up all important data before performing any system update
  2. For iPhone/iPad: Go to Settings > General > Software Update and install iOS 14.7 or later
  3. For Mac: Go to System Preferences > Software Update and install macOS Big Sur 11.5 or later, or Security Update 2021-004 for macOS Catalina
  4. For Apple Watch: On your iPhone, open the Watch app > My Watch > General > Software Update and install watchOS 7.6 or later
  5. For Apple TV: Go to Settings > System > Software Updates and install tvOS 14.7 or later
  6. After updating, verify the update was successful by checking the system version
Caveat Standard OS update - backup recommended before updating; some older applications may not be compatible with newer OS versions

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

Fix this in Iphone Os 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-2021-30776 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