Debian LinuxOperating system · Debian
CVE-2021-1871
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 logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
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 logic vulnerability in WebKit affecting iOS, iPadOS, and macOS that allows a remote attacker to achieve arbitrary code execution through malicious web content. This was being actively exploited in the wild as a zero-day vulnerability.
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
Debian LinuxOperating system
= 10.0
FedoraOperating system
= 33< 14.4< 14.4>= 10.15, < 10.15.7= 10.15.7>= 11.0.1, < 11.2CVSS 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 checksWork through these to decide whether this CVE applies to you.
-
Check macOS versionGo to Apple menu > About This Mac to see the macOS version number (e.g., 10.15.7, 11.0.1, 11.1)Affected if Running macOS 10.15.x (any version up to and including 10.15.7) or macOS 11.0.1 through 11.1.x (anything below 11.2)
-
Check iOS/iPadOS versionOpen Settings > General > About on the device to view the iOS version (e.g., 14.3, 14.3.1)Affected if Running iOS or iPadOS version lower than 14.4 (any 14.x version below 14.4, or any earlier version)
-
Check Linux distribution versionRun 'cat /etc/os-release' or 'lsb_release -a' to identify the Linux distribution and versionAffected if Running Debian 10.0 exactly or Fedora 33 exactly, with WebKit-based browsers installed
-
Identify WebKit-based browsers on LinuxRun 'dpkg -l | grep -i webkit' (Debian) or 'rpm -qa | grep -i webkit' (Fedora) to list installed WebKit packagesAffected if WebKit packages are installed on a Debian 10.0 or Fedora 33 system
-
Check Safari WebKit version (macOS)Open Safari, go to Safari > About Safari, or inspect /System/Library/Frameworks/WebKit.framework for version infoAffected if Safari is using a WebKit version tied to a vulnerable macOS release (10.15.x or 11.0.1-11.1.x)
You are affected if your device runs macOS 10.15.x, macOS 11.0.1-11.1.x, iOS/iPadOS below 14.4, Debian 10.0, or Fedora 33, and you use WebKit-based browsers to browse the web.
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 data10.15.711.214.4
Immediately apply the available security updates: iOS 14.4, iPadOS 14.4, macOS Big Sur 11.2, Security Update 2021-001 for Catalina, and Security Update 2021-001 for Mojave. Prioritize external-facing devices and any systems processing untrusted web content.
Fix this in Debian Linux
Exploited in the wild — priority engagement
- Consultation3.0 h
- Implementation8.0 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 $4,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1871 — 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-2021-1871 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