Site Isolation Bypass via Crafted MHTML in Google Chrome

Publication date: 2026-05-28

Last updated on: 2026-06-03

Assigner: Chrome

Description

Insufficient validation of untrusted input in Site Isolation in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted MHTML page. (Chromium security severity: High)

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-05-28

Last Modified

2026-06-03

Generated

2026-07-09

AI Q&A

2026-05-29

EPSS Evaluated

2026-07-08

NVD

CVE-2026-9903

EUVD

EUVD-2026-33198

Affected Vendors & Products

Vendor	Product	Version / Range
google	chrome	to 148.0.7778.216 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-20	The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

Attack-Flow Graph

Executive Summary

This vulnerability involves insufficient validation of untrusted input in the Site Isolation feature of Google Chrome versions prior to 148.0.7778.216. It allows a remote attacker who has already compromised the renderer process to bypass site isolation by using a specially crafted MHTML page.

Impact Analysis

An attacker exploiting this vulnerability can bypass site isolation protections in Google Chrome, potentially allowing them to access or manipulate data from other sites or processes that should be isolated. This could lead to unauthorized data access or compromise of browser security.

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