---
id: "CVE-2026-91379"
kind: "vulnerability"
aliases: ["CVE-2026-91379"]
title: "Oracle Java SE: JDK tools flaw lets a local attacker alter data"
severity: "medium"
cvss: 4.7
epss: 0.00118
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["applets", "graalvm", "java", "java-web-start", "oracle-jdk", "runtime"]
not_affected_if: ["no-web-start-or-applets", "server-only", "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-2026-91379", "first_seen_at": "2026-10-23T21:57:26+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91379", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Oracle Java SE: JDK tools flaw lets a local attacker alter data

A flaw in the JDK tools component of Oracle Java SE and GraalVM lets an attacker with local logon modify critical data, with a person other than the attacker needing to take an action. The description says it matters mainly for clients running sandboxed Java Web Start applets or untrusted code, and does not apply to servers running only trusted code.

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

## How to check

- Run `java -version` and compare the build to the affected releases listed in the advisory: Java SE 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27; GraalVM for JDK 17.0.20.1 and 21.0.12.1; GraalVM Enterprise Edition 21.3.19.1.1.
- Check whether any sandboxed Java Web Start or applet deployment loads untrusted code on those machines.

## Fix

- Update Oracle Java SE and GraalVM for JDK to a patched release from the Oracle Critical Patch Update for this quarter.
- Update GraalVM Enterprise Edition to a patched build; the sources do not name the fixed version.

## Timeline

- 2026-10-23T21:57:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91379
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91379

## From the sources

Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition product of Oracle Java SE (component: JDK tools).  Supported versions that are affected are Oracle Java SE: 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 logon to the infrastructure where Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition executes 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 creation, deletion or modification access to critical data or 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 4.7 (Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/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_