CVE-2026-9309

Name: CVE-2026-9309
Creator: NVD / NIST
Published: 2026-06-01T13:16:33.623+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.16%

Last modified Jun 17, 2026

CVE-2026-9309 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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. EPSS estimates a 0.16% chance of exploitation in the next 30 days.

Description

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. This vulnerability was fixed in Firefox for iOS 151.2.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS Probability

0.16%

5.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 151.2

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2036573Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-53/Vendor Advisory

Timeline

Published: Jun 1, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-9309?

How severe is CVE-2026-9309?

CVE-2026-9309 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.16% probability of exploitation in the next 30 days.

How do I fix CVE-2026-9309?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-9309?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST