dbcve.org
Mac Os XOperating system · Apple

CVE-2021-1834

CRITICAL · 9.8 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 11.3 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. A malicious application may be able to execute arbitrary code with kernel privileges.

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

A kernel-level out-of-bounds write vulnerability in macOS allows a malicious application to execute arbitrary code with kernel privileges. The vulnerability stems from insufficient bounds checking in kernel memory operations.

MitigationApply the relevant Apple security updates: macOS Big Sur 11.3, Security Update 2021-002 for Catalina, or Security Update 2021-003 for Mojave, depending on the affected system version.

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:= 10.14= 10.14.0= 10.14.1= 10.14.2= 10.14.3= 10.14.4= 10.14.5= 10.14.6= 10.15= 10.15.1= 10.15.2= 10.15.3
macOSOperating system
Affected:>= 11.0, < 11.3

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 checks

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

  1. Identify installed macOS version
    Open Terminal and run 'sw_vers -productVersion' to display the exact macOS version number
    Affected if The version number falls within 10.14.x, 10.15.x, or 11.0-11.2.x (less than 11.3)
  2. Confirm major macOS release name
    Run 'sw_vers -productName' to verify whether the system is macOS Mojave (10.14), Catalina (10.15), or Big Sur (11.x)
    Affected if The system runs Mojave, Catalina, or Big Sur versions prior to 11.3
  3. Verify kernel version as secondary indicator
    Run 'uname -r' to check the kernel release number; for Big Sur this typically shows 20.x, for Catalina 19.x, for Mojave 18.x
    Affected if Kernel version corresponds to an affected macOS release (18.x for Mojave, 19.x for Catalina, 20.x for Big Sur prior to 11.3)
  4. Check if security update was applied
    Review the output of 'system_profiler SPSoftwareDataType' or check System Preferences > About > System Report for installed security updates
    Affected if The system shows security update 2021-003 (Mojave), 2021-002 (Catalina), or macOS 11.3 or later as NOT installed

A system is affected if it runs macOS X 10.14.x, 10.15.x, or macOS 11.0-11.2.x and lacks the corresponding security update (2021-003, 2021-002, or 11.3 respectively).

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.

dbcve · scoped
Upgrade available Upgrade to 11.3 or later
Fixed in 11.3
Interim mitigation

Apply the relevant Apple security updates: macOS Big Sur 11.3, Security Update 2021-002 for Catalina, or Security Update 2021-003 for Mojave, depending on the affected system version.

Recommended fix High confidence

macOS Big Sur 11.3+ or Security Update 2021-002 (Catalina) / Security Update 2021-003 (Mojave)

  1. Open System Preferences (or System Settings on macOS Ventura and later)
  2. Click on Software Update to check for available updates
  3. For macOS Big Sur 11.0-11.2: Update to macOS Big Sur 11.3 or later
  4. For macOS Catalina (10.15.x): Install Security Update 2021-002
  5. For macOS Mojave (10.14.x): Install Security Update 2021-003
  6. Restart the system after applying the security update
Caveat Standard risk associated with applying system updates; backup recommended before updating

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mac Os X Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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Scan for this in your stack

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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-2021-1834 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