CVE-2021-30761
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 memory corruption issue was addressed with improved state management. This issue is fixed in iOS 12.5.4. 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 confidenceMemory corruption vulnerability in WebKit (iOS browser engine) triggered by processing maliciously crafted web content, leading to arbitrary code execution. Addressed through improved state management. Actively exploited zero-day affecting iOS 12.5.3 and earlier.
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< 12.5.4CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check iOS version on the deviceOpen Settings app, go to General > About, and note the version number displayed next to 'Version'Affected if The version shown is 12.5.3 or earlier (anything below 12.5.4)
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Confirm device model is supported by iOS 12Verify the device can run iOS 12 by checking Settings > General > About > Model Name. Devices that received the 12.5.4 update include iPhone 5s, iPhone 6, iPhone 6 Plus, iPad Air, iPad mini 2, iPad mini 3, and iPod touch (6th generation)Affected if Device model is capable of iOS 12 but is running a version lower than 12.5.4
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Identify if Safari or any app using WebKit is usedWebKit is the rendering engine used by Safari and all third-party browsers on iOS. No configuration check needed - WebKit is always present on iOS devicesAffected if Device runs any version of iOS below 12.5.4 and has Safari or any browser app installed (all iOS devices have this by default)
A device is affected if it is running any version of iOS 12.5.3 or earlier, as the vulnerability exists in WebKit which is inherent to Safari on all such versions.
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 · scoped12.5.4
Apply iOS 12.5.4 or later security update to affected devices immediately. This is a critical priority given confirmed active exploitation in the wild.
iOS 12.5.4
- Back up your iPhone device before performing any update
- Connect your iPhone to power and ensure stable Wi-Fi connection
- Open Settings app on the device
- Navigate to General > Software Update
- Locate and select iOS 12.5.4 update
- Tap Download and Install
- Enter passcode if prompted and confirm the installation
- Allow the device to complete the update process and restart
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30761 — 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-2021-30761 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
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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