CVE-2026-9903

chromium-browser: Insufficient validation of untrusted input in Site Isolation

Published May 28, 2026 CVSS 3.1 · 5 Medium EPSS < 1% KEV · Not listed
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)

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6316-1 chromium security update
History
Type Values Removed Values Added
CPEs cpe:2.3:a:google:chrome:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 8.7, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L'}

Type Values Removed Values Added
Title Remote bypass of site isolation via crafted MHTML page chromium-browser: Insufficient validation of untrusted input in Site Isolation
Weaknesses CWE-1173
References
Metrics threat_severity

None

cvssV3_1

{'score': 8.7, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N'}

threat_severity

Important

Type Values Removed Values Added
Title Remote bypass of site isolation via crafted MHTML page
Type Values Removed Values Added
First Time appeared Google
Google chrome
Vendors & Products Google
Google chrome
Type Values Removed Values Added
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)
Weaknesses CWE-20
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Chrome
Published
Updated
May 29, 2026, 5:40 PM
Reserved
May 28, 2026, 5:24 PM
Status
Analyzed
Published
May 28, 2026, 11:16 PM
Modified
Jul 21, 2026, 11:10 AM
Severity
Important
Public date
May 27, 2026, 12:00 AM