Mitigation Bypass in Firefox DOM Security Component

Publication date: 2026-01-13

Last updated on: 2026-06-30

Assigner: Mozilla Corporation

Description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS Scores

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Meta Information

Published

2026-01-13

Last Modified

2026-06-30

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-0877

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 147 (exc)
mozilla	firefox_esr	to 115.32 (exc)
mozilla	firefox_esr	to 140.7 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-693	The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.

Attack-Flow Graph

Executive Summary

CVE-2026-0877 is a high-impact security vulnerability in Firefox browsers involving a mitigation bypass in the Document Object Model (DOM) security component. This flaw allows attackers to circumvent existing security measures within the DOM, potentially enabling unauthorized actions or code execution within the browser environment. [1, 2, 3]

Impact Analysis

This vulnerability can impact you by allowing attackers to bypass security mitigations in the DOM, which may lead to unauthorized actions or exploitation such as executing malicious code within your browser. This can compromise your browser's security and potentially expose sensitive information or allow further attacks. [1, 2, 3]

Mitigation Strategies

To mitigate this vulnerability, you should update your Firefox browser to version 147 or later, or if you are using Firefox ESR, update to ESR 115.32 or later, or ESR 140.7 or later. These versions include fixes that address the mitigation bypass in the DOM security component. [1, 2, 3]

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