CVE-2021-1878
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 integer overflow was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. An attacker in a privileged network position may be able to leak sensitive user information.
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 confidenceAn integer overflow vulnerability in Apple macOS that could allow an attacker with privileged network position to leak sensitive user information. The vulnerability was addressed through improved input validation in the affected macOS versions.
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>= 10.14, <= 10.14.5>= 10.15, <= 10.15.5= 10.14.6= 10.15.6= 10.15.7>= 11.0, < 11.3CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/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.
-
Check macOS versionRun 'sw_vers -productVersion' in Terminal to get the exact macOS version numberAffected if The version is 10.14.6, 10.15.6, 10.15.7, or any 10.14.x through 10.15.5, or falls between 11.0 and 11.2.x (inclusive)
-
Verify security update statusCheck System Preferences > Security & Privacy > General for the 'Your computer is up to date' message, or run 'system_profiler SPSoftwareDataType' to see installed security updatesAffected if No security update from 2021 (such as Security Update 2021-002, 2021-003, or Big Sur 11.3) is installed on vulnerable versions
-
Identify network exposureReview running network services and listeners via 'netstat -an' or System Preferences > Sharing to see which network features are enabledAffected if The system has network-facing services enabled and is running a vulnerable macOS version without the security update
A user is affected if they are running any macOS version between 10.14 and 10.15.7, or between 11.0 and 11.2.x, without the corresponding 2021 security updates installed.
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 · scoped11.3
Apply the relevant macOS security update: Big Sur 11.3, Security Update 2021-002 for Catalina, or Security Update 2021-003 for Mojave.
macOS Big Sur 11.3+ or apply platform-specific Security Update 2021-002 (Catalina) / 2021-003 (Mojave)
- Check current macOS version: Apple menu > About This Mac
- If running macOS Big Sur (11.x), upgrade to macOS 11.3 or later via Software Update
- If running macOS Catalina (10.15), apply Security Update 2021-002 via Apple menu > System Preferences > Software Update
- If running macOS Mojave (10.14), apply Security Update 2021-003 via Apple menu > System Preferences > Software Update
- After updating, verify the fix is applied by checking System Preferences > Software Update for no further relevant updates
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1878 — 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-2021-1878 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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