CVE-2026-84129

What it is

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

At a glance

Exploitability

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

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

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

Timeline

1. 2026-09-01 13:20 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-03 12:54 UTC Last updatedMost recent change to the record

Details

Published

2026-09-01 13:20 UTC

Last modified

2026-09-03 12:54 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-346

Record status

Analyzed

Affected

• Mozilla Firefox < 153.2.0
• Mozilla Firefox < 155.0.0
• Mozilla Thunderbird < 153.2.0
• Mozilla Thunderbird < 155.0

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High