CVE-2026-91398 in Java SE
Summary
by MITRE • 10/21/2026
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).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the Networking component of Oracle Java SE, as well as Oracle GraalVM for JDK and Oracle GraalVM Enterprise Edition versions including 8u503, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27, and their corresponding enterprise variants. This flaw is characterized by a logic error or improper validation mechanism within the SOCKS5 proxy implementation that allows an unauthenticated attacker to exploit the system over a network connection. The attack vector requires no user interaction and does not necessitate prior authentication, making it particularly dangerous in environments where Java applications are exposed to external networks or when clients connect through proxied connections. Although the description notes that exploitation is difficult due to high complexity requirements for the attacker, the potential impact remains severe because it bypasses standard security controls designed to isolate untrusted code from critical system resources.
From a technical perspective, this vulnerability represents an integrity violation where malicious actors can manipulate data flows or state within the Java runtime environment via SOCKS5 connections. The flaw likely stems from insufficient validation of proxy requests or improper handling of connection states, allowing an attacker to inject unauthorized commands or alter existing processes. This aligns with CWE-20 Improper Input Validation and potentially CWE-918 Server-Side Request Forgery if the vulnerability allows the Java application to make unintended network connections on behalf of the user. The ability to compromise these components means that any data processed by the affected Java applications, including sensitive corporate information or personal data handled by sandboxed applets, is at risk of unauthorized modification, deletion, or creation. This directly impacts the integrity aspect of the CIA triad, which is reflected in the CVSS 3.1 base score of 6.8 with a high impact on integrity and scope change indicating that damage extends beyond the immediate application to other products relying on the compromised Java runtime.
The operational impact of this vulnerability is significant for organizations deploying Oracle Java SE or GraalVM, particularly those running sandboxed Java Web Start applications or applets that load untrusted code from the internet. These deployments traditionally rely on the Java sandbox model to restrict access to local resources; however, a successful exploit can break out of these restrictions by manipulating network connections through the SOCKS5 interface. This could lead to data exfiltration, modification of critical configuration files, or installation of additional malware if combined with other vulnerabilities. The scope change noted in the advisory implies that an attacker leveraging this flaw might pivot into adjacent systems or services connected via the compromised Java instance, thereby expanding the blast radius beyond the initial target application. This is consistent with ATT&CK technique T1071 Application Layer Protocol abuse, where attackers use legitimate protocols like SOCKS to evade detection and establish command-and-control channels or move laterally within a network.
Mitigation strategies must prioritize immediate patching of all affected Oracle Java SE, GraalVM for JDK, and GraalVM Enterprise Edition versions to the latest available updates provided by Oracle. Organizations should review their deployment configurations to ensure that SOCKS5 proxies are not exposed to untrusted networks unless absolutely necessary, implementing strict access control lists if such services must remain active. For environments running sandboxed Java applets or Web Start applications, it is critical to enforce code signing and verify the integrity of all loaded classes before execution. Additionally, network segmentation should be employed to limit the ability of compromised systems to communicate with external SOCKS proxies, thereby reducing the attack surface. Security teams should also monitor for anomalous network traffic patterns indicative of SOCKS tunneling or unauthorized proxy usage as part of their intrusion detection and prevention systems to identify potential exploitation attempts in real time.