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Iphone OsOperating system · Apple

CVE-2021-30789

HIGH · 7.8 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 7.6 / 11.5 or later.
See remediation →
81/100
Remediation priority · High
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 out-of-bounds read was addressed with improved input 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. Processing a maliciously crafted font file 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

An out-of-bounds read vulnerability in Apple's font parsing subsystem that could be exploited by processing a maliciously crafted font file, potentially leading to arbitrary code execution. The vulnerability was addressed through improved input validation.

MitigationUpdate all affected Apple devices (iOS, macOS, watchOS, tvOS) to the patched versions (iOS 14.7+, macOS Big Sur 11.5+, watchOS 7.6+, tvOS 14.7+, or Security Update 2021-004 Catalina+) or later.

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>= 11.0, < 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
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 Apple device type and operating system
    On iOS: Settings > General > About > Model Name. On macOS: Apple menu > About This Mac > System Report > Hardware overview. On tvOS/watchOS: Settings > General > About.
    Affected if The device runs iOS, macOS, tvOS, or watchOS from the affected product list.
  2. Check the installed iOS version
    On iPhone/iPad: Go to Settings > General > About > Software Version. Look for the iOS version number (e.g., 14.6). Compare this against the affected range: versions less than 14.7 are vulnerable.
    Affected if The iOS version is any version below 14.7.
  3. Check the installed macOS version
    On Mac: Apple menu > About This Mac. The macOS version will display (e.g., 11.4, 10.15.7). For 10.15.x, also run 'sw_vers' in Terminal to confirm the exact build. Compare against affected ranges: macOS Big Sur versions below 11.5, or macOS Catalina 10.15.7 and any 10.15.x between 10.15 and 10.15.6.
    Affected if macOS Big Sur is below 11.5, or macOS Catalina is 10.15.7 or any version from 10.15 through 10.15.6.
  4. Check the installed tvOS or watchOS version
    On Apple TV: Settings > General > About > tvOS Version. On Apple Watch: Open the Watch app on iPhone > General > About > watchOS Version. Compare against affected range: versions below 14.7 for tvOS, below 7.6 for watchOS.
    Affected if tvOS version is below 14.7, or watchOS version is below 7.6.
  5. Verify if the system can process font files
    The vulnerability triggers when parsing a maliciously crafted font file. This is a built-in capability of the font parsing subsystem. No specific configuration check is needed as font parsing is enabled by default in all affected versions.
    Affected if The system can open or preview font files (this is true by default on unpatched systems).

A user is affected if they are running any iOS, macOS, tvOS, or watchOS version that falls within the affected ranges: iOS/tvOS/watchOS below 14.7/7.6 respectively, or macOS Big Sur below 11.5, or macOS Catalina 10.15.x (any version from 10.15 through 10.15.7).

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

Update all affected Apple devices (iOS, macOS, watchOS, tvOS) to the patched versions (iOS 14.7+, macOS Big Sur 11.5+, watchOS 7.6+, tvOS 14.7+, or Security Update 2021-004 Catalina+) or later.

Recommended fix High confidence

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

  1. Identify the affected Apple device (iPhone, iPad, Mac, Apple Watch, or Apple TV)
  2. Check the current operating system version on the device
  3. For iPhone/iPad: Upgrade to iOS 14.7 or later via Settings > General > Software Update
  4. For Mac: Upgrade to macOS Big Sur 11.5 or later (or apply Security Update 2021-004 for Catalina) via System Preferences > Software Update
  5. For Apple Watch: Upgrade to watchOS 7.6 or later via the Watch app on iPhone
  6. For Apple TV: Upgrade to tvOS 14.7 or later via Settings > System > Software Updates
  7. After updating, verify the new OS version matches or exceeds the fixed release
Caveat Upgrading to newer major OS versions may introduce compatibility issues with older applications or require significant UI changes; backup device data before updating

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

Fix this in Iphone Os Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,560
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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-2021-30789 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