CVE-2012-3989

What it is

Mozilla Firefox before 16.0, Thunderbird before 16.0, and SeaMonkey before 2.13 do not properly perform a cast of an unspecified variable during use of the instanceof operator on a JavaScript object, which allows remote attackers to execute arbitrary code or cause a denial of service (assertion failure) via a crafted web site.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

3.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2012-10-10 17:55 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 23:44 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.5% in the next 30 days (EPSS).
• Severity: 9.3 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2012-10-10 17:55 UTC

Last modified

2026-06-16 23:44 UTC

Exploit probability

3.5% · EPSS, next 30 days

Weakness

CWE-119 · Buffer errors

Record status

Modified

Affected

• Mozilla Firefox < 16.0
• Mozilla Seamonkey < 2.13
• Mozilla Thunderbird < 16.0
• Canonical Ubuntu Linux 10.04
• Canonical Ubuntu Linux 11.04
• Canonical Ubuntu Linux 11.10
• Canonical Ubuntu Linux 12.04
• Suse Linux Enterprise Desktop 10

Attack profile CVSS 2.0 · 9.3

Attack vector

Network

Complexity

Medium

Authentication

None

Confidentiality

Complete

Integrity

Complete

Availability

Complete

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-2012-3989.md and follow it. Check whether this project is affected by CVE-2012-3989. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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