CVE-2016-4644
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 · uneditedIn iOS before 9.3.3, tvOS before 9.2.2, and OS X El Capitan before v10.11.6 and Security Update 2016-004, a downgrade issue existed with HTTP authentication credentials saved in Keychain. This issue was addressed by storing the authentication types with the credentials.
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 downgrade vulnerability existed in iOS, tvOS, and OS X El Capitan where HTTP authentication credentials stored in Keychain did not preserve the authentication type (e.g., Basic, Digest, NTLM). This allowed potential downgrade attacks where credentials could be reused with weaker or different authentication mechanisms, as the system could not distinguish the original authentication type.
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< 9.2.2< 9.3.3>= 10.11.0, < 10.11.6CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Check iOS version on iPhone or iPadGo to Settings > General > About and look at the 'Version' fieldAffected if The version is earlier than 9.3.3 (for example, 9.3.2, 9.3.1, 9.3, 9.2.x, etc.)
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Check tvOS version on Apple TVGo to Settings > General > About and look at the 'Version' fieldAffected if The version is earlier than 9.2.2 (for example, 9.2.1, 9.2, 9.1, etc.)
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Check macOS El Capitan versionClick the Apple menu > About This Mac. The version number appears below the macOS name. Alternatively, run 'sw_vers' in TerminalAffected if The build version is 10.11.0 through 10.11.5, or the version shows 10.11.x where x is less than 6
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Identify HTTP authentication credentials in Keychain (optional confirmation)On macOS, open Keychain Access, select 'login' keychain, and search for items with 'http' in the name or that are of kind 'Network password'. On iOS, this requires jailbreak access to inspect keychain dumpAffected if Any HTTP, web or network passwords are stored in Keychain on an affected OS version
You are affected if your device runs iOS earlier than 9.3.3, tvOS earlier than 9.2.2, or macOS El Capitan 10.11.0 through 10.11.5, and you have HTTP authentication credentials stored in Keychain.
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 data9.2.29.3.310.11.6
Apply the vendor patches: iOS 9.3.3 or later, tvOS 9.2.2 or later, OS X El Capitan v10.11.6 or Security Update 2016-004.
- Consultation1.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-4644 — 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-2016-4644 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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- 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
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