FirefoxWeb browser · Mozilla
CVE-2016-5284
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 · uneditedMozilla Firefox before 49.0, Firefox ESR 45.x before 45.4, and Thunderbird < 45.4 rely on unintended expiration dates for Preloaded Public Key Pinning, which allows man-in-the-middle attackers to spoof add-on updates by leveraging possession of an X.509 server certificate for addons.mozilla.org signed by an arbitrary built-in Certification Authority.
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 confidenceMozilla Firefox and Thunderbird implemented Preloaded Public Key Pinning (HPKP) for addons.mozilla.org with unintended expiration dates. Once these pins expired, the pinning protection was no longer enforced, allowing a man-in-the-middle attacker with any X.509 certificate for addons.mozilla.org signed by a built-in Certification Authority to intercept and spoof add-on updates.
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
FirefoxWeb browser
<= 48.0.2= 45.0= 45.0.1= 45.0.2= 45.1.1= 45.2.0= 45.3.0CVSS 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
- Changed
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/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 Firefox versionGo to Help > About Firefox or navigate to about:support to view the version numberAffected if The version is 45.0, 45.0.1, 45.0.2, 45.1.1, 45.2.0, 45.3.0, or any version 48.0.2 or earlier
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Check Thunderbird versionGo to Help > About Thunderbird to view the version numberAffected if The version matches the same affected Firefox version range (45.x series or 48.0.2 and earlier)
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Verify HPKP pinning status for addons.mozilla.orgNavigate to addons.mozilla.org in the browser, click the padlock icon in the address bar, view connection details, and check if Public Key Pinning is listed as activeAffected if HPKP is shown as not enforced or not pinned for this domain, indicating the expired pins are not protecting the connection
You are affected if your Firefox or Thunderbird version is 45.0.x, 45.1.x, 45.2.x, 45.3.x, or any version up to and including 48.0.2, and you access addons.mozilla.org for add-on updates.
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 dataUpgrade to Firefox 49.0 or later, Firefox ESR 45.4 or later, or Thunderbird 45.4 or later to receive the patched HPKP implementation with corrected pin expiration handling.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-5284 — 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-2016-5284 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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