CVE-2026-91463 in GraalVM Enterprise Edition
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: JGSS). 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 multiple protocols 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 access to critical data or complete access to 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 5.3 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the Java GSS-API, commonly referred to as JGSS, a core component of Oracle Java SE and its associated GraalVM distributions. This security flaw affects multiple supported versions including Oracle Java SE 8u503 through 27, Oracle GraalVM for JDK 17.0.20.1 and 21.0.12.1, as well as Oracle GraalVM Enterprise Edition 21.3.19.1.1. The JGSS module is responsible for handling authentication and security context establishment in Java applications that utilize the Generic Security Services Application Program Interface. This component enables interoperability with various underlying security mechanisms such as Kerberos or SPNEGO, facilitating secure communication across networked systems.
The technical nature of this flaw allows an unauthenticated attacker to compromise the affected software via multiple protocols over a network connection. While the vulnerability is classified as difficult to exploit due to high complexity requirements, it does not require prior authentication on the target system. The attack vector leverages specific interactions within the JGSS implementation where improper handling of security tokens or context states can lead to unauthorized access. This aligns with CWE-20 Improper Input Validation and potentially CWE-787 Out-of-bounds Write if memory corruption is involved, though the primary impact described points toward information disclosure rather than code execution.
The operational impact of a successful exploitation is significant for client-side deployments but limited in server contexts. The vulnerability enables unauthorized access to critical data or complete access to all accessible data within the Java environment. This corresponds directly to high confidentiality impacts as reflected in the CVSS 3.1 base score of 5.3, with vectors indicating network accessibility, no required privileges, and a requirement for user interaction. It is crucial to note that this vulnerability primarily affects client-side deployments where sandboxed Java Web Start applications or applets load untrusted code from the internet. In these scenarios, the application relies on the Java sandbox security model which can be bypassed through this flaw.
Conversely, the risk profile changes drastically for server-side deployments. Oracle explicitly states that this vulnerability does not apply to typical server environments where only trusted code installed by an administrator is loaded and executed. Therefore, enterprise servers running standard backend services are generally unaffected unless they specifically utilize client-like JGSS interactions with untrusted external entities in a manner that mimics the vulnerable client behavior. This distinction highlights the importance of deployment context when assessing risk exposure for this specific CVE.
Mitigation strategies should focus on restricting access to Java-enabled applications and ensuring strict adherence to security policies regarding applet execution. Organizations running affected versions must evaluate whether their deployments involve untrusted code loading scenarios typical of web clients. If such usage is present, immediate patching to the latest available version listed in Oracle Critical Patch Update advisories is recommended. Additionally, administrators should enforce Java Security settings that restrict or disable unsigned applets and Web Start applications where possible. For environments unable to upgrade immediately, network-level controls can help mitigate risk by blocking access from untrusted sources to systems running vulnerable JGSS implementations. Continuous monitoring for anomalous authentication attempts via GSS-API mechanisms is also advised to detect potential exploitation activities aligned with ATT&CK techniques related to credential dumping or unauthorized service interaction.