CVE-2021-30735
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 · uneditedA malicious application may be able to execute arbitrary code with kernel privileges. This issue is fixed in macOS Big Sur 11.4, Security Update 2021-003 Catalina, Security Update 2021-004 Mojave. An out-of-bounds write issue was addressed with improved bounds checking.
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 confidenceAn out-of-bounds write vulnerability in the macOS kernel allows a malicious application to write beyond allocated memory bounds, enabling arbitrary code execution with kernel-level privileges.
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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Identify the installed macOS versionRun 'sw_vers -productVersion' in Terminal to get the exact version number (e.g., 10.15.7, 11.3.1)Affected if The version falls within the affected ranges: 10.14.0-10.14.5, 10.14.6, 10.15.0-10.15.6, 10.15.7, or 11.0.1-11.3.x (any version below 11.4)
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Confirm the major macOS release nameRun 'sw_vers -productName' to determine if the system is running macOS High Sierra (10.13), Mojave (10.14), Catalina (10.15), or Big Sur (11)Affected if The release is Mojave (10.14), Catalina (10.15), or Big Sur (11.x) as these are the affected product lines
You are affected if your macOS version is 10.14.x (Mojave), 10.15.x (Catalina), or 11.0.1 through 11.3.x (Big Sur prior to 11.4), as these versions contain the vulnerable kernel code.
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 relevant Apple security update: macOS Big Sur 11.4, Security Update 2021-003 (Catalina), or Security Update 2021-004 (Mojave) to patch the kernel vulnerability.
macOS Big Sur 11.4 or later; Security Update 2021-003 for Catalina; Security Update 2021-004 for Mojave
- Identify the current macOS version by clicking the Apple menu and selecting About This Mac
- For macOS Big Sur (11.x) users: Update to macOS Big Sur 11.4 or later via System Preferences > Software Update
- For macOS Catalina (10.15.x) users: Apply Security Update 2021-003 Catalina via System Preferences > Software Update
- For macOS Mojave (10.14.x) users: Apply Security Update 2021-004 Mojave via System Preferences > Software Update
- Restart the system after applying the update to ensure the kernel patch is fully applied
- Verify the update was successfully installed by checking System Preferences > Security & Privacy > General
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30735 — 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-2021-30735 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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