---
id: "CVE-2026-91451"
kind: "vulnerability"
aliases: ["CVE-2026-91451"]
title: "Oracle Java SE: Networking flaw lets unauthenticated remote users alter some data"
severity: "medium"
cvss: 5.3
epss: 0.00282
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["graalvm", "java", "oracle-jdk", "runtime", "self-hosted", "web-services"]
not_affected_if: ["applets-and-web-start-only", "no-untrusted-network-input"]
published_at: "2026-10-20T22:20:48+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-2026-91451", "first_seen_at": "2026-10-23T21:57:27+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91451", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Oracle Java SE: Networking flaw lets unauthenticated remote users alter some data

A flaw in the Networking component of Oracle Java SE lets an unauthenticated attacker over the network change or delete some data the Java application can access. The attack works by supplying data to APIs in that component, such as through a web service, and does not need Java Web Start or applets.

_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: 8u503, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, and GraalVM 17.0.20.1, 21.0.12.1, 21.3.19.1.1.
- Check whether any service built on Java parses untrusted network input through the Networking APIs.

## Fix

- Oracle Java SE: move to a patched release from Oracle's April 2026 Critical Patch Update (the exact fixed builds are unknown from these sources).
- Oracle GraalVM: move to a patched GraalVM release for your line.

## Timeline

- 2026-10-23T21:57:27+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91451
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91451

## From the sources

Vulnerability in Oracle Java SE (component: Networking).  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; Oracle GraalVM for JDK: 17.0.20.1 and  21.0.12.1; 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.  Successful attacks of this vulnerability can result in  unauthorized update, insert or delete access to some of Oracle Java SE accessible data. Note: This vulnerability can only be exploited by supplying data to APIs in the specified Component without using Untrusted Java Web Start applications or Untrusted Java applets, such as through a web service. CVSS 3.1 Base Score 5.3 (Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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_