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.
CVE-2016-5284
Score 7.4 from GitHub Security Advisory (severity: HIGH) published 2022-05-14. NVD baseline CVSS 7.4; sources differ by 0.0.
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.4
- EG Score
- 7.4(medium)
- EG Risk
- 39(Track)EG Risk 39/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity74% × 45%Exploitation2% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 2%
- EPSS %ILE
- 83%
- KEV
- Not listed
Published
September 22, 2016
Last Modified
June 17, 2026
References (26)
- security@mozillahttp://rhn.redhat.com/errata/RHSA-2016-1912.html
- security@mozillahttp://seclists.org/dailydave/2016/q3/51
- security@mozillahttp://www.debian.org/security/2016/dsa-3674
- security@mozillahttp://www.mozilla.org/security/announce/2016/mfsa2016-85.html
- security@mozillahttp://www.oracle.com/technetwork/topics/security/linuxbulletinoct2016-3090545.html
- security@mozillahttp://www.securityfocus.com/bid/93049
- security@mozillahttp://www.securitytracker.com/id/1036852
- security@mozillahttps://blog.mozilla.org/security/2016/09/16/update-on-add-on-pinning-vulnerability/
- security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1303127
- security@mozillahttps://hackernoon.com/tor-browser-exposed-anti-privacy-implantation-at-mass-scale-bd68e9eb1e95
- security@mozillahttps://security.gentoo.org/glsa/201701-15
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2016-86/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2016-88/
- af854a3a-2127-422b-91ae-364da2661108http://rhn.redhat.com/errata/RHSA-2016-1912.html
- af854a3a-2127-422b-91ae-364da2661108http://seclists.org/dailydave/2016/q3/51
Patch Availability(3)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| ubuntu | firefox-testsuite (49.0+build4-0ubuntu0.16.04.1) @ xenial | 2026-05-22 | ubuntu |
| ubuntu | thunderbird (1:45.4.0+build1-0ubuntu0.16.10.1) @ yakkety | 2026-05-22 | ubuntu |
| redhat | firefox-0:45.4.0-1.el7_2 | 2016-09-21 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(6 across 6 ecosystems)
Debian:11(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | — | 45.4.0esr-1 | — |
Debian:12(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | — | 45.4.0esr-1 | — |
Debian:13(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | — | 45.4.0esr-1 | — |
Debian:14(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | — | 45.4.0esr-1 | — |
Debian:7(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | 45.0.1esr-1 ... 45.3.0esr-2 (13 versions) | 45.4.0esr-1~deb7u1 | — |
Debian:8(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| firefox-esr | 45.0.1esr-1 ... 45.4.0esr-1~deb8u1 (16 versions) | 45.4.0esr-1~deb8u2 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
All Vendor Advisories
(3)
Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.
Data Freshness Timeline
(refreshed 5× in last 7d / 17× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
Showing the most recent 100 of 148 total refreshes for this CVE.
- 2026-09-24 13:59 UTCEPSS rescore
- 2026-09-23 13:41 UTCEPSS rescore
- 2026-09-19 15:35 UTCEPSS rescore
- 2026-09-18 20:06 UTCOSV refresh
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- 2026-08-16 02:09 UTCEPSS rescore
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Related CVEs(same product + same vendor + same CWE)
Same product
10 shownDebian:7:firefox-esr
Same vendor
10 shownredhat:RHSA-2016:1912
- CVE-2016-5281EG 9.8EPSS p92CRITICAL
- CVE-2016-5280EG 9.8EPSS p92CRITICAL
- CVE-2016-5277EG 9.8EPSS p90CRITICAL
- CVE-2016-5276EG 9.8EPSS p90CRITICAL
- CVE-2016-5274EG 9.8EPSS p90CRITICAL
- CVE-2016-5270EG 9.8EPSS p90CRITICAL
- CVE-2016-5257EG 9.8EPSS p91CRITICAL
- CVE-2016-5278EG 8.8EPSS p90HIGH
- CVE-2016-5272EG 8.8HIGH
- CVE-2016-5250EG 4.3MEDIUM
Frequently asked(5)
What is CVE-2016-5284?
When was CVE-2016-5284 disclosed?
Is CVE-2016-5284 actively exploited?
What is the CVSS score of CVE-2016-5284?
How do I remediate CVE-2016-5284?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2016-5284
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