CVE-2021-30728
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 11.4, Security Update 2021-003 Catalina, Security Update 2021-004 Mojave. A malicious application may be able to execute arbitrary code with kernel privileges.
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 confidenceCVE-2021-30728 is an out-of-bounds write vulnerability in the macOS kernel that allows a malicious application to execute arbitrary code with kernel-level privileges. The issue was addressed through improved bounds checking in the affected macOS versions.
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>= 10.14.0, <= 10.14.5>= 10.15, <= 10.15.6= 10.14.6= 10.15.7>= 11.0.1, < 11.4CVSS 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 installed macOS versionRun 'sw_vers -productVersion' in Terminal or view System Preferences > About This MacAffected if Version is 10.14.0 through 10.14.5, 10.14.6, 10.15 through 10.15.6, 10.15.7, or 11.0.1 through 11.3.x (any version below 11.4 on Big Sur, below 10.14.6 on Mojave, or below 10.15.7 on Catalina)
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Confirm macOS release name for clarityRun 'sw_vers -productVersionExtra' in Terminal to see the marketing name (Mojave, Catalina, or Big Sur)Affected if Any of the vulnerable version ranges from step 1 apply to your installed release
You are affected if your system runs any macOS version within the ranges 10.14.0-10.14.5, 10.14.6, 10.15-10.15.6, 10.15.7, or 11.0.1-11.3.x; macOS 11.4 and later, macOS 10.14.6 with the security update, and macOS 10.15.7 with the security update are not affected.
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.
dbcve · scoped11.4
Apply the appropriate Apple security update: macOS Big Sur 11.4, Security Update 2021-003 for Catalina, or Security Update 2021-004 for Mojave.
macOS Big Sur 11.4 or later; Security Update 2021-003 Catalina; Security Update 2021-004 Mojave
- Identify your current macOS version by clicking the Apple menu and selecting About This Mac
- For macOS 10.14.x (Mojave): Install Security Update 2021-004 by going to System Preferences > Software Update
- For macOS 10.15.x (Catalina): Install Security Update 2021-003 by going to System Preferences > Software Update
- For macOS 11.x (Big Sur): Upgrade to macOS 11.4 or later by going to System Preferences > Software Update
- Restart the system after applying the update to ensure the kernel patch takes effect
- Verify the update was successfully installed by checking About This Mac again
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30728 — 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-2021-30728 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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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.
- 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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