---
id: "CVE-2026-91464"
kind: "vulnerability"
aliases: ["CVE-2026-91464"]
title: "Oracle Java SE: JGSS flaw exposes data to untrusted-code attackers"
severity: "medium"
cvss: 5.3
epss: 0.00281
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["desktop-java", "graalvm", "java", "jgss", "runtime"]
not_affected_if: ["no-applets-or-web-start", "server-only-trusted-code"]
published_at: "2026-10-20T22:20:50+00:00"
first_seen_at: "2026-10-23T21:57:27+00:00"
updated_at: "2026-10-25T12:38:52+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91464", "first_seen_at": "2026-10-23T21:57:27+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91464", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Oracle Java SE: JGSS flaw exposes data to untrusted-code attackers

A flaw in the JGSS component of Oracle Java SE and GraalVM lets a remote attacker reach confidential data when a user runs untrusted code. Oracle rates it medium (CVSS 5.3) and says it matters mainly for sandboxed Java Web Start or applet deployments.

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

## How to check

- Run `java -version` to see the installed Java SE build and compare it with the affected versions listed in the advisory.
- Check whether the deployment runs sandboxed Java Web Start applications or applets that load untrusted code from the internet.

## Fix

- Move Java SE 8 to `8u503` or later, Java 11 to `11.0.32.1` or later, Java 17 to `17.0.20.1` or later, Java 21 to `21.0.12.1` or later, and Java 25 to `25.0.4.1` or later, per Oracle's patch list.
- Move GraalVM for JDK 17 to `17.0.20.1` or later and 21 to `21.0.12.1` or later, and GraalVM Enterprise to `21.3.19.1.1` or later.

## Timeline

- 2026-10-23T21:57:27+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91464
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91464

## From the sources

Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition product of Oracle Java SE (component: JGSS).  Supported versions that are affected are Oracle Java SE: 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27; Oracle GraalVM for JDK: 17.0.20.1 and  21.0.12.1; Oracle GraalVM Enterprise Edition: 21.3.19.1.1. Difficult to exploit vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE, Oracle GraalVM for JDK, 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 access to critical data or complete access to all Oracle Java SE, Oracle GraalVM for JDK, 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 5.3 (Confidentiality impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/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_