dbcve.org
Mac Os XOperating system · Apple

CVE-2020-3866

MEDIUM · 5.5 CVSS v3.1 Published 2020-02-27
Fix available
A fix is available. Upgrade to 10.15.3 or later.
See remediation →
58/100
Remediation priority · Elevated
No privileges

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 · unedited
This was addressed with additional checks by Gatekeeper on files mounted through a network share. This issue is fixed in macOS Catalina 10.15.3. Searching for and opening a file from an attacker controlled NFS mount may bypass Gatekeeper.

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 confidence

Gatekeeper, macOS's application whitelisting security feature, can be bypassed when a user searches for and opens a file from an attacker-controlled NFS (Network File System) mount. The vulnerability exists because Gatekeeper was not applying proper security checks to files accessed via NFS network shares, allowing unsigned or malicious code to execute.

MitigationUpgrade to macOS Catalina 10.15.3 or later, which includes the fix. Avoid mounting NFS shares from untrusted or attacker-controlled sources until systems are patched.

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
Mac Os XOperating system
Affected:< 10.15.3

CVSS 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
None
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check macOS version
    Open Terminal and run 'sw_vers -productVersion' to see the installed macOS version
    Affected if Version is below 10.15.3 (e.g., 10.15.2, 10.15.1, 10.15.0)
  2. Identify mounted NFS shares
    Open Terminal and run 'showmount -e' or check 'mount' output for nfs type mounts (mount | grep nfs)
    Affected if Any NFS shares are currently mounted from a network source
  3. Verify Gatekeeper status
    Open Terminal and run 'spctl --status' to confirm Gatekeeper is enabled
    Affected if Gatekeeper is disabled (output shows 'assessor disabled')
  4. Check for recent NFS file access
    Open Terminal and run 'ls -la /mnt' or 'df' to list mounted network volumes, then check Spotlight search history or recent documents for files opened from NFS paths
    Affected if Files were recently opened from an NFS-mounted directory

The environment is affected if macOS version is below 10.15.3 AND an NFS share from an untrusted source is mounted AND a user has opened files from that NFS location.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 10.15.3 or later
Fixed in 10.15.3
Interim mitigation

Upgrade to macOS Catalina 10.15.3 or later, which includes the fix. Avoid mounting NFS shares from untrusted or attacker-controlled sources until systems are patched.

Fix this in Mac Os X Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-3866 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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