SafariWeb browser · Apple
CVE-2016-7152
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 · uneditedThe HTTPS protocol does not consider the role of the TCP congestion window in providing information about content length, which makes it easier for remote attackers to obtain cleartext data by leveraging a web-browser configuration in which third-party cookies are sent, aka a "HEIST" attack.
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 confidenceThe HEIST attack exploits the HTTPS protocol's failure to account for TCP congestion window behavior as an information leak about content length. Attackers can determine the size of encrypted responses by measuring TCP window sizes, then combine this with third-party cookie behavior in browsers to extract cleartext data from HTTPS responses.
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
all versions
FirefoxWeb browser
all versions
ChromeWeb browser
all versionsall versionsall versionsall versionsCVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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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Identify browser type and versionOpen the browser, navigate to its about/help section or settings to display the full version number (e.g., Chrome: Settings > Help > About Chrome; Firefox: Menu > Help > About Firefox)Affected if The browser is Safari, Firefox, Chrome, Opera, Edge, or Internet Explorer regardless of version - all versions are affected by this design flaw
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Check third-party cookie settings in the browserNavigate to browser privacy/cookie settings. In Chrome: Settings > Privacy and security > Third-party cookies. In Firefox: Settings > Privacy & Security > Enhanced Tracking Protection. In Safari: Preferences > Privacy > Prevent cross-site tracking. Look for whether third-party cookies are allowed or blocked.Affected if Third-party cookies are enabled or set to 'Allow' - this is the required condition for the HEIST attack to extract data via cookie-based mechanisms
The environment is affected if the browser is any version of Safari, Firefox, Chrome, Opera, Edge, or Internet Explorer AND third-party cookies are currently enabled in browser settings.
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 dataDisable third-party cookies in browser settings to prevent the attack vector. Server-side mitigations are limited as this is a fundamental HTTPS/TCP design issue requiring browser or protocol-level fixes.
Fix this in Safari
Scoped from the published advisory
- Consultation8.0 h
- Implementation4.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,320.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-7152 — 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-2016-7152 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
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