CVE-2026-9309: Arbitrary JavaScript execution in internal pages via Reader View JSON-LD injection

Published Jun 1, 2026
·
Updated

Firefox for iOS Reader View did not properly escape HTML tags in JSON-LD metadata. A malicious page could inject markup that changed Reader View behavior and leaked sensitive URL parameters. These parameters could then be used to access internal pages, potentially resulting in arbitrary JavaScript execution in an internal origin.

Affected Software

3 affected components
All of the following
Mozilla Firefox=151.2
Apple iOS
Mozilla Firefox Iphone Os<151.2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Firefox for iOS to a version that resolves this vulnerability.

    Fixed in 151.2

Event History

Jun 1, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·11:24 AM
Data Sourced
via MITRE·11:24 AM
Description
Data Sourced
via NVD·01:16 PM
DescriptionSeverityWeaknessAffected Software
Jun 29, 58424
Event
via FIRST·10:09 AM

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-9309?

CVE-2026-9309 has a medium severity rating of 5.4 based on the CVSS v3.1 scoring system.

2

How do I fix CVE-2026-9309?

To mitigate CVE-2026-9309, update to the latest version of Mozilla Firefox for iOS that addresses this vulnerability.

3

What type of vulnerability is CVE-2026-9309?

CVE-2026-9309 is an arbitrary JavaScript execution vulnerability caused by improper escaping of HTML tags in JSON-LD metadata.

4

What could be the consequences of CVE-2026-9309?

If exploited, CVE-2026-9309 could lead to the execution of arbitrary JavaScript and disclosure of sensitive URL parameters.

5

Which software is affected by CVE-2026-9309?

CVE-2026-9309 affects Mozilla Firefox on iOS.

Company

Resources

Contact

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