---
id: "CVE-2026-91385"
kind: "vulnerability"
aliases: ["CVE-2026-91385"]
title: "Java SE JavaFX: untrusted applet or Web Start code can read and change data"
severity: "medium"
cvss: 5.4
epss: 0.00181
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["applets", "desktop-clients", "graalvm", "java", "javafx", "runtime", "web-start"]
not_affected_if: ["no-applets-or-web-start", "server-only-java", "trusted-code-only"]
published_at: "2026-10-20T22:20:41+00:00"
first_seen_at: "2026-10-23T21:57:26+00:00"
updated_at: "2026-10-25T12:38:52+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91385", "first_seen_at": "2026-10-23T21:57:26+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91385", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Java SE JavaFX: untrusted applet or Web Start code can read and change data

A flaw in the JavaFX component of Oracle Java SE lets an unauthenticated remote attacker affect data in Java deployments that run untrusted code in sandboxed Web Start applications or applets. Successful exploitation needs a person to take an action, and the attacker gets limited read and write access to some data.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `java -version` and compare against the affected Java SE 8u503 line.
- Check for JavaFX `21.0.12`, `25.0.4` or `27` and GraalVM Enterprise `21.3.19.1.1`.
- Look for sandboxed Java Web Start or applet use on client machines.

## Fix

- Move Java SE to a patched release from Oracle's July 2026 Critical Patch Update advisory.
- Move JavaFX to a patched release newer than `21.0.12`, `25.0.4` or `27`.
- Move GraalVM Enterprise to a patched release newer than `21.3.19.1.1`.

## Timeline

- 2026-10-23T21:57:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91385
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91385

## From the sources

Vulnerability in the Oracle Java SE, Oracle JavaFX, Oracle GraalVM Enterprise Edition product of Oracle Java SE (component: JavaFX).  Supported versions that are affected are Oracle Java SE: 8u503; Oracle JavaFX: 21.0.12, 25.0.4 and  27;  Oracle GraalVM Enterprise Edition: 21.3.19.1.1. Easily exploitable vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE, Oracle JavaFX, Oracle GraalVM Enterprise Edition.  Successful attacks require human interaction from a person other than the attacker. Successful attacks of this vulnerability can result in  unauthorized update, insert or delete access to some of Oracle Java SE, Oracle JavaFX, Oracle GraalVM Enterprise Edition accessible data as well as  unauthorized read access to a subset of Oracle Java SE, Oracle JavaFX, Oracle GraalVM Enterprise Edition accessible data. Note: This vulnerability applies to Java deployments, typically in clients running sandboxed Java Web Start applications or sandboxed Java applets, that load and run untrusted code (e.g., code that comes from the internet) and rely on the Java sandbox for security. This vulnerability does not apply to Java deployments, typically in servers, that load and run only trusted code (e.g., code installed by an administrator). CVSS 3.1 Base Score 5.4 (Confidentiality and Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N).

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_