CVE-2021-30845
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 read was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.6. A local user may be able to read kernel memory.
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 · moderate confidenceA kernel-level out-of-bounds read vulnerability in macOS Big Sur allows a local authenticated user to read arbitrary kernel memory due to insufficient bounds checking in a kernel component. This information disclosure vulnerability could potentially aid in further privilege escalation.
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>= 11.0, < 11.6CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
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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Determine installed macOS versionClick Apple menu > About This Mac, or run 'sw_vers' in TerminalAffected if Version is 11.0 through 11.5.x (any 11.x version below 11.6)
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Confirm kernel versionRun 'uname -r' in Terminal to see the kernel release numberAffected if Kernel version corresponds to a Big Sur release below 11.6 (typically 20.x range for 11.x)
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Check system update statusRun 'softwareupdate -l' or check System Preferences > Software UpdateAffected if Updates to 11.6 or later are available or marked as installed
If macOS Big Sur 11.0 through 11.5.x is installed and has not been updated to 11.6 or later, the system is vulnerable to kernel memory disclosure.
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 · scoped11.6
Apply macOS Big Sur 11.6 or later security update. For systems that cannot update immediately, consider restricting local user access or implementing additional monitoring until patching is feasible.
macOS Big Sur 11.6
- Open System Preferences (or System Settings on macOS Ventura and later)
- Click on "Software Update" to check for available updates
- If macOS Big Sur 11.6 is available, click "Update Now" to download and install the security update
- Alternatively, download macOS Big Sur 11.6 from the Apple Support website and run the installer manually
- Restart the computer after the update completes to ensure the security fix is fully applied
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30845 — 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-2021-30845 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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