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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2021.
FedoraOperating system · Fedoraproject

CVE-2021-1870

CRITICAL · 9.8 CVSS v3.1 Published 2021-04-02
Fix available
A fix is available. Upgrade to 2.30.6 / 10.15.7 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild 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
A 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 · moderate confidence

A logic issue in Apple operating systems (macOS, iOS, iPadOS) allowed remote attackers to achieve arbitrary code execution through improved restrictions bypass. This was a client-side vulnerability that could be exploited via malicious web content or network vectors.

MitigationApply the vendor-supplied patches: macOS Big Sur 11.2, Security Update 2021-001 for Catalina/Mojave, iOS 14.4, or iPadOS 14.4. Given active exploitation, prioritize patching internet-facing and high-value assets immediately.

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
FedoraOperating system
Affected:= 32= 33
IpadosOperating system
Affected:< 14.4
Iphone OsOperating system
Affected:< 14.4
Mac Os XOperating system
Affected:>= 10.15, < 10.15.7= 10.15.7
macOSOperating system
Affected:>= 11.0.1, < 11.2
WebkitgtkWeb browser
Affected:< 2.30.6

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. Check iOS/iPadOS version on Apple mobile devices
    Go to Settings > General > About and note the version number. Alternatively, use idevicesysdiag or check via Apple Configurator or MDM.
    Affected if Version is less than 14.4 (for example, 14.3, 14.2, 14.1, 14.0, or earlier)
  2. Check macOS version on Apple computers
    Click Apple menu > About This Mac and note the version number. Alternatively, run 'sw_vers' in Terminal.
    Affected if Version is 10.15.7 or any 10.15.x version before 10.15.7, OR version is 11.0.1 through 11.1 (any 11.0.x or 11.1, but not 11.2 or later)
  3. Check WebKitGTK version on Linux systems with Fedora
    Run 'rpm -qa | grep webkit2gtk' or 'dnf list installed webkit2gtk' to list the installed webkit2gtk package version.
    Affected if Version is earlier than 2.30.6 (for example, 2.30.5, 2.30.4, etc.)
  4. Verify if WebKit-based browsers or apps are in use
    On affected Apple devices, check for Safari or any app that embeds WebKit. On Fedora Linux, check for applications using webkit2gtk such as Epiphany, Geary, or other WebKit-based software.
    Affected if WebKit-based browsers or apps are actively used and the underlying OS package version is vulnerable per the checks above

A user is affected if they run any Apple iOS device below 14.4, Apple iPadOS device below 14.4, Apple macOS 10.15.x before 10.15.7 or macOS 11.0.1-11.1, Fedora 32 or 33 with webkit2gtk below 2.30.6, and actively use WebKit-based applications or browsers on those systems.

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 2.30.6 / 10.15.7 / 11.2 or later
Fixed in 2.30.610.15.711.2
Interim mitigation

Apply the vendor-supplied patches: macOS Big Sur 11.2, Security Update 2021-001 for Catalina/Mojave, iOS 14.4, or iPadOS 14.4. Given active exploitation, prioritize patching internet-facing and high-value assets immediately.

Recommended fix High confidence

iOS 14.4+, iPadOS 14.4+, macOS 11.2+, Security Update 2021-001, WebKitGTK 2.30.6+

  1. For iOS devices: Go to Settings > General > Software Update and upgrade to iOS 14.4 or later
  2. For iPadOS devices: Go to Settings > General > Software Update and upgrade to iPadOS 14.4 or later
  3. For macOS Big Sur (11.x): Go to System Preferences > Software Update and upgrade to macOS 11.2 or later, or apply Security Update 2021-001
  4. For macOS Catalina (10.15.7): Apply Security Update 2021-001 Catalina via System Preferences > Software Update
  5. For WebKitGTK-based browsers on Linux: Upgrade webkit2gtk to version 2.30.6 or later via system package manager (e.g., dnf update webkit2gtk)
  6. For Fedora systems: Upgrade to Fedora 34 or later which contains the fixed WebKitGTK package
Caveat Major OS version upgrades (e.g., Fedora 32/33 to 34) may introduce behavioral changes; backup data before upgrading

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

Fix this in Fedora Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2021-1870 in production — separate from our analysis above.

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.

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