CVE-2026-6755

Received Received - Intake

Mitigation Bypass in Firefox DOM postMessage Component

Publication date: 2026-04-21

Last updated on: 2026-04-22

Assigner: Mozilla Corporation

Description

Mitigation bypass in the DOM: postMessage component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-04-21

Last Modified

2026-04-22

Generated

2026-07-06

AI Q&A

2026-04-21

EPSS Evaluated

2026-07-04

NVD

CVE-2026-6755

EUVD

EUVD-2026-24096

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 150.0 (exc)
mozilla	thunderbird	to 150.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-352	The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.

Attack-Flow Graph

Executive Summary

This vulnerability is a mitigation bypass in the DOM postMessage component of Mozilla Firefox. It means that a security measure intended to protect the postMessage functionality in the Document Object Model (DOM) could be circumvented by an attacker. The issue was fixed in Firefox version 150.

Impact Analysis

Exploitation of this vulnerability could allow an attacker to bypass security mitigations related to the postMessage component in Firefox. This might lead to unauthorized communication or data exchange between different origins in the browser, potentially exposing sensitive information or enabling further attacks.

Mitigation Strategies

The vulnerability is fixed in Firefox version 150. Immediate mitigation should include updating Firefox to version 150 or later.

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