CVE-2016-5284

What it is

Mozilla 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.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure.

Exploit odds

2.4% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2016-09-22 22:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:49 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.4% in the next 30 days (EPSS).
• Severity: 7.4 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2016-09-22 22:59 UTC

Last modified

2026-06-17 00:49 UTC

Exploit probability

2.4% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Mozilla Firefox ≤ 48.0.2
• Mozilla Firefox 45.0
• Mozilla Firefox 45.0.1
• Mozilla Firefox 45.0.2
• Mozilla Firefox 45.1.1
• Mozilla Firefox 45.2.0
• Mozilla Firefox 45.3.0

Attack profile CVSS 3.0 · 7.4

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

Required

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-5284.md and follow it. Check whether this project is affected by CVE-2016-5284. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge