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

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.

Published: 2026-06-01 Last update: 2026-06-03 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-9309 is rated Low Risk (25.5/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.04%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-9309

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-02 — 0.04% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-9309

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.5 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-9309

GitHub Security Advisory for CVE-2026-9309

GHSA-29fm-4hpp-5p7g · Severity: medium — Firefox for iOS Reader View did not properly escape HTML tags in JSON-LD metadata. A malicious...

Affected software / configurations for CVE-2026-9309

Vendor Product Version Raw CPE
mozilla firefox < 151.2 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:iphone_os:*:*

References for CVE-2026-9309

cvelogic Threat Intelligence