---
id: "CVE-2026-91394"
kind: "vulnerability"
aliases: ["CVE-2026-91394"]
title: "Oracle Java SE: Networking flaw exposes data to unauthenticated network attackers"
severity: "medium"
cvss: 5.9
epss: 0.00332
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["graalvm", "java", "oracle-jdk", "runtime", "web-services"]
not_affected_if: ["default-config", "patched-version"]
published_at: "2026-10-20T22:20:42+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-2026-91394", "first_seen_at": "2026-10-23T21:57:26+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91394", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Oracle Java SE: Networking flaw exposes data to unauthenticated network attackers

A flaw in the Networking component of Oracle Java SE and Oracle GraalVM for JDK lets an unauthenticated attacker with network access read sensitive data from a Java application. Exploitation is difficult and can run through a web service that passes data into the affected APIs.

_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 releases: Java SE 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27, and GraalVM for JDK 17.0.20.1 and 21.0.12.1.
- Check whether any Java Web Start or applet deployments load untrusted code, since the sources say this also applies there.

## Fix

- Oracle Java SE: move to a patched release from the Oracle Critical Patch Update for the affected line, such as `11.0.32.1`, `17.0.20.1`, `21.0.12.1`, or `25.0.4.1`, or to a release that includes the fix.
- Oracle GraalVM for JDK: move to `17.0.20.1` or `21.0.12.1` or later.
- Java SE 27 is listed as affected; the sources do not give a patched 27 build, so unknown.

## Timeline

- 2026-10-23T21:57:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91394
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91394

## From the sources

Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK product of Oracle Java SE (component: Networking).  Supported versions that are affected are Oracle Java SE: 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. Difficult to exploit vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE, Oracle GraalVM for JDK.  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 accessible data. Note: This vulnerability can be exploited by using APIs in the specified Component, e.g., through a web service which supplies data to the APIs. This vulnerability also 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. CVSS 3.1 Base Score 5.9 (Confidentiality impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/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_