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SafariWeb browser · Apple

CVE-2021-30823

MEDIUM · 6.5 CVSS v3.1 Published 2021-10-28
Fix available
A fix is available. Upgrade to 8.0 / 12.0.1 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 Monterey 12.0.1, iOS 14.8 and iPadOS 14.8, tvOS 15, Safari 15, watchOS 8. An attacker in a privileged network position may be able to bypass HSTS.

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

CVE-2021-30823 is a logic flaw in Apple's HSTS (HTTP Strict Transport Security) implementation that allows an attacker with privileged network position (e.g., man-in-the-middle) to bypass HSTS protections. This enables the attacker to downgrade HTTPS connections to HTTP, exposing sensitive traffic. The vulnerability affects macOS Monterey 12.0.1 and earlier, iOS/iPadOS 14.8 and earlier, tvOS 15 and earlier, Safari 15 and earlier, and watchOS 8 and earlier.

MitigationApply the vendor-supplied patches: update to macOS Monterey 12.0.1+, iOS/iPadOS 14.8+, tvOS 15+, Safari 15+, and watchOS 8+ as appropriate for each affected device.

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
SafariWeb browser
Affected:< 15.0.0
IpadosOperating system
Affected:< 14.8
Iphone OsOperating system
Affected:< 14.8
macOSOperating system
Affected:< 12.0.1
TvosOperating system
Affected:< 15.0
WatchosOperating system
Affected:< 8.0

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Apple device and operating system
    Determine whether the device is a Mac, iPhone/iPad, Apple TV, or Apple Watch. On Mac, go to Apple menu > About This Mac. On iPhone/iPad, go to Settings > General > About. On Apple TV, go to Settings > General > About. On Apple Watch, open the Watch app on iPhone and go to General > About.
    Affected if Device runs any of the affected Apple operating systems listed below
  2. Check macOS version on Mac computers
    Open Terminal and run: sw_vers -productVersion. Alternatively, go to Apple menu > About This Mac and note the version number (e.g., 12.0, 11.6, etc.).
    Affected if Version is lower than 12.0.1 (e.g., 12.0, 11.x, 10.x)
  3. Check iOS or iPadOS version on iPhone or iPad
    Go to Settings > General > About and note the version number displayed next to 'Version' (e.g., 14.7, 14.6, etc.).
    Affected if Version is lower than 14.8 (e.g., 14.7, 14.6, 13.x, etc.)
  4. Check Safari version on macOS
    Open Safari, go to Safari menu > About Safari. The version number appears in the window that opens (e.g., 14.1.2, 15.0, etc.).
    Affected if Version is lower than 15.0.0 (e.g., 14.1.2, 14.0, 13.x)
  5. Check tvOS version on Apple TV
    Go to Settings > General > About and note the version number (e.g., 14.7, 14.6, etc.).
    Affected if Version is lower than 15.0 (e.g., 14.7, 14.6, 13.x)
  6. Check watchOS version on Apple Watch
    On Apple Watch, go to Settings > General > About and note the version. Alternatively, open the Watch app on paired iPhone, go to General > About, and check the watchOS version.
    Affected if Version is lower than 8.0 (e.g., 7.6, 7.5, 6.x, etc.)

The environment is affected if any installed Apple operating system or Safari version falls below the thresholds: macOS 12.0.1, iOS/iPadOS 14.8, tvOS 15.0, watchOS 8.0, or Safari 15.0.0.

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 8.0 / 12.0.1 / 14.8 or later
Fixed in 8.012.0.114.8
Interim mitigation

Apply the vendor-supplied patches: update to macOS Monterey 12.0.1+, iOS/iPadOS 14.8+, tvOS 15+, Safari 15+, and watchOS 8+ as appropriate for each affected device.

Recommended fix High confidence

macOS Monterey 12.0.1, iOS 14.8, iPadOS 14.8, tvOS 15.0, watchOS 8.0, Safari 15

  1. For macOS users: Update to macOS Monterey 12.0.1 via System Preferences > Software Update
  2. For iPhone users: Update to iOS 14.8 via Settings > General > Software Update
  3. For iPad users: Update to iPadOS 14.8 via Settings > General > Software Update
  4. For Apple TV users: Update to tvOS 15.0 via Settings > System > Software Updates
  5. For Apple Watch users: Update to watchOS 8.0 via the Watch app on iPhone > General > Software Update
  6. For Safari: Update via macOS update (Safari 15 is included in macOS Monterey 12.0.1)
Caveat Routine security update; may include minor UI or feature changes typical of point releases

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

Fix this in Safari Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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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-2021-30823 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