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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-2021-30858

HIGH · 8.8 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to 11.6 / 12.5.5 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges

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 use after free issue was addressed with improved memory management. This issue is fixed in iOS 14.8 and iPadOS 14.8, macOS Big Sur 11.6. Processing maliciously crafted web content may lead to 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 confidence

A use-after-free vulnerability in WebKit allows processing of maliciously crafted web content to trigger memory corruption leading to arbitrary code execution. This is a memory management flaw that can be exploited remotely without user interaction beyond visiting a malicious webpage.

MitigationApply the available security updates: iOS 14.8 and later, iPadOS 14.8 and later, or macOS Big Sur 11.6 and later. Prioritize patching given active exploitation in the wild.

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:= 33= 34
Debian LinuxOperating system
Affected:= 10.0= 11.0
IpadosOperating system
Affected:>= 13.1, < 14.8
Iphone OsOperating system
Affected:< 12.5.5>= 13.0, < 14.8
macOSOperating system
Affected:< 11.6

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 the operating system and product
    Determine if the device runs Apple iOS, iPadOS, macOS, Fedora, or Debian Linux, as these are the affected products listed for this CVE
    Affected if The device runs any of the listed affected operating systems or Linux distributions
  2. Check iOS or iPadOS version on Apple mobile devices
    On iPhone or iPad, go to Settings > General > About to view the version number. Compare against the affected ranges: iOS < 12.5.5 OR >= 13.0 and < 14.8; iPadOS >= 13.1 and < 14.8
    Affected if The iOS version is less than 12.5.5, or is 13.x through 14.7.x; OR the iPadOS version is 13.1 through 14.7.x
  3. Check macOS version on Apple computers
    Click the Apple menu > About This Mac to view the macOS version. Compare against affected range: macOS < 11.6 (any version before Big Sur 11.6)
    Affected if The macOS version is 11.5.x or earlier, or any version of Catalina (10.15.x) or earlier
  4. Check for WebKitGTK on Fedora or Debian Linux
    On Fedora, run: rpm -qa | grep -i webkit. On Debian, run: dpkg -l | grep -i webkit. This checks if the WebKit rendering engine package is installed
    Affected if WebKitGTK package is installed on Fedora 33 or 34, or Debian 10.0 or 11.0, and the package version is unpatched
  5. Verify if Safari or any app uses WebKit for web content
    On macOS/iOS, confirm Safari is used or check if third-party apps embed WebView components that render web content. On Linux, check if applications use webkit2gtk (such as GNOME Web, evolution, or other GTK webviews)
    Affected if Safari or any WebKit-based application processes untrusted web content on a vulnerable OS version

A defender is affected if their iOS/iPadOS device runs a version before 14.8, their macOS device runs a version before 11.6, or their Fedora/Debian system has an unpatched WebKitGTK package installed, AND they process untrusted web content through Safari or a WebKit-based application.

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 11.6 / 12.5.5 / 14.8 or later
Fixed in 11.612.5.514.8
Interim mitigation

Apply the available security updates: iOS 14.8 and later, iPadOS 14.8 and later, or macOS Big Sur 11.6 and later. Prioritize patching given active exploitation in the wild.

Recommended fix High confidence

iOS 14.8+, iPadOS 14.8+, macOS Big Sur 11.6+

  1. For iOS devices: Go to Settings > General > Software Update and upgrade to iOS 14.8 or later
  2. For iPadOS devices: Go to Settings > General > Software Update and upgrade to iPadOS 14.8 or later
  3. For macOS devices: Go to System Preferences > Software Update and upgrade to macOS Big Sur 11.6 or later
  4. After updating, verify the version in Settings/About to confirm the update was applied
Caveat Ensure backups are created before updating; some older apps may be incompatible with the new OS version

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

Fix this in Fedora Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.

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-2021-30858 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