CVE-2021-1776
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 · uneditedAn out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, watchOS 7.3, tvOS 14.4, iOS 14.4 and iPadOS 14.4. 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 confidenceThis is an out-of-bounds write vulnerability in Apple's font parsing subsystem. Processing a maliciously crafted font file allows an attacker to write data beyond allocated buffer boundaries, which can be leveraged to achieve arbitrary code execution on the affected device.
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< 14.4< 14.4>= 10.14, < 10.14.6>= 10.15, < 10.15.7= 10.14.6= 10.15.7>= 11.0, < 11.2< 14.4< 7.3CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check iOS/iPadOS versionOn the device, go to Settings > General > About > Version. Alternatively, connect to a computer with iTunes or Finder and check the device info, or use the `idevicesyslog` tool if available.Affected if The version number is less than 14.4 (for example, 14.3, 14.2, etc.) or shows a version from the 13.x line.
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Check macOS versionOpen System Preferences > About, or run `sw_vers` in Terminal. Note both the major version number (like 10.14, 10.15, or 11.x) and the specific build number.Affected if The version is 10.14.x and less than 10.14.6; OR version is 10.15.x and less than 10.15.7; OR version is 11.0.x and less than 11.2.
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Check tvOS versionOn Apple TV, go to Settings > About > Version. The tvOS version will be displayed.Affected if The version number is less than 14.4 (for example, 14.3, 14.2, etc.).
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Check watchOS versionOn the paired iPhone, open the Watch app, go to General > About, and scroll to view the watchOS version. Alternatively, check directly on the Apple Watch via Settings > About.Affected if The version number is less than 7.3 (for example, 7.2, 7.1, 7.0, etc.).
A device is affected if its operating system version falls within any of the unpatched version ranges listed for that product, regardless of how font files are processed.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor data7.310.14.610.15.7
Apply the applicable security updates (macOS Big Sur 11.2, Security Update 2021-001 for Catalina/Mojave, watchOS 7.3, tvOS 14.4, iOS 14.4/iPadOS 14.4) to all affected Apple devices to remediate this vulnerability.
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1776 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-1776 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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