CVE-2020-9939
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 · uneditedThis issue was addressed with improved checks. This issue is fixed in macOS Catalina 10.15.6. A local user may be able to load unsigned kernel extensions.
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 vulnerability in macOS Catalina allowed local users to bypass code signing checks and load unsigned kernel extensions (kexts). Kernel extensions run with kernel-level privileges, so this bypass could enable privilege escalation or malicious code execution at the highest privilege level. The issue was fixed in macOS 10.15.6 with improved validation checks.
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< 10.15.6CVSS 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
- High
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/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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Verify macOS versionOpen Terminal and run 'sw_vers -productVersion' to get the installed macOS versionAffected if The version returned is less than 10.15.6 (e.g., 10.15, 10.15.5, 10.15.4, etc.)
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Inspect loaded kernel extensionsRun 'kextstat | grep -v com.apple' in Terminal to list third-party kernel extensions, then manually verify each has a valid code signature using 'codesign -dv /path/to/kext.kext'Affected if Any third-party kext lacks a valid code signature or shows signature validation errors
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Review kernel extension loading logsRun 'log show --predicate 'subsystem == "com.apple.kext"' --last 30d' to examine kext loading events, looking for entries indicating failed signature validation or unsigned kext loadsAffected if Logs show successful loads of unsigned kexts or repeated signature validation failures
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Check system integrity protection statusRun 'csrutil status' in Terminal to confirm System Integrity Protection is enabledAffected if System Integrity Protection is disabled (this increases exploitability but does not confirm exploitation)
The system is affected if it runs macOS version lower than 10.15.6 and shows evidence of unsigned kernel extensions or anomalous kext loading in system logs.
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.
From vendor data10.15.6
Apply macOS Catalina 10.15.6 or later security update to affected systems. For systems that cannot be patched, audit system integrity and kernel extension loading logs to detect any prior exploitation of unsigned kext loading.
- Consultation2.0 h
- Implementation4.0 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-2020-9939 — 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-2020-9939 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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