---
id: "CVE-2026-91398"
kind: "vulnerability"
aliases: ["CVE-2026-91398"]
title: "Oracle Java SE: SOCKS5 networking flaw lets unauthenticated attackers modify data"
severity: "medium"
cvss: 6.8
epss: 0.0023
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["backend", "graalvm", "java", "jvm", "runtime", "self-hosted"]
not_affected_if: ["default-config", "no-socks5-proxy", "trusted-code-only"]
published_at: "2026-10-20T22:20:43+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-2026-91398", "first_seen_at": "2026-10-23T21:57:26+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91398", "first_seen_at": "2026-10-25T12:38:52+00:00"}]
---

# Oracle Java SE: SOCKS5 networking flaw lets unauthenticated attackers modify data

Oracle Java SE and GraalVM have a networking flaw in the SOCKS5 proxy handling that is hard to exploit. An unauthenticated attacker on the network can write or change data that the Java application can reach.

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

## How to check

- Run `java -version` and compare the output with the fixed releases listed in the Fix section.
- Check whether the application or JVM uses SOCKS5 proxy settings (for example `socksProxyHost` or `socksProxyPort` system properties).

## Fix

- Move Oracle Java SE 8 to `8u503` or later (or the performance build `8u503-perf`).
- Move Oracle Java SE 11 to `11.0.32.1` or later.
- Move Oracle Java SE 17 to `17.0.20.1` or later and Oracle GraalVM for JDK 17 to `17.0.20.1` or later.
- Move Oracle Java SE 21 and Oracle GraalVM for JDK 21 to `21.0.12.1` or later, Oracle Java SE 25 to `25.0.4.1` or later, and Oracle GraalVM Enterprise Edition 21 to `21.3.19.1.1` or later.

## Timeline

- 2026-10-23T21:57:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91398
- 2026-10-25T12:38:52+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91398

## From the sources

Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition product of 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, 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 SOCKS5 to compromise Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition.  While the vulnerability is in Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition, attacks may significantly impact additional products (scope change).  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 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 6.8 (Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N).

---

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