CVE-2021-30817
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 permissions issue was addressed with improved validation. This issue is fixed in macOS Big Sur 11.5. A malicious application may be able to access data about the accounts the user is using Family Sharing with.
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 confidenceA permissions validation issue in macOS Big Sur's Family Sharing feature allowed malicious local applications to bypass access controls and read sensitive account information about Family Sharing participants.
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< 11.5CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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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Check installed macOS versionClick the Apple menu > About This Mac. Look for the version number under the macOS name (e.g., 11.4, 11.3, 11.2.2). Alternatively, run 'sw_vers -productVersion' in Terminal.Affected if The version is lower than 11.5 (e.g., 11.4, 11.3, 11.2, 11.1, 11.0) or shows a build number earlier than the 11.5 security update.
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Verify if Family Sharing is enabledOpen System Preferences (or System Settings on newer macOS) > Family Sharing. Check if Family Sharing is turned on or if any family members are listed.Affected if Family Sharing is enabled and configured with family members, as this is the configuration the vulnerability exploits.
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Confirm Family Sharing service statusRun 'familyshared' process check: 'ps aux | grep -i family' in Terminal to see if the Family Sharing daemon is running.Affected if The Family Sharing daemon (familyshared) is actively running on the system.
A system is affected if it runs macOS version 11.4 or earlier AND has Family Sharing enabled, allowing a local malicious application to potentially read Family Sharing participant information.
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 · scoped11.5
Update to macOS Big Sur 11.5 or later, which contains the corrected permission validation for Family Sharing data.
macOS Big Sur 11.5 or later
- Check the current macOS version by clicking the Apple menu and selecting About This Mac
- Back up important data using Time Machine or another backup method
- Open System Preferences and select Software Update to check for available updates
- If macOS 11.5 or later is available, click Download and Install to upgrade
- If automatic updates are available, enable them to receive future security patches
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30817 — 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-2021-30817 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
- No spam, self-promotion, credentials, or personal data