CVE-2026-91334 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: ImageIO). 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 of this vulnerability can result in unauthorized read access to a subset of 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 3.7 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the ImageIO component of Oracle Java SE, as well as in supported versions of Oracle GraalVM for JDK and Oracle GraalVM Enterprise Edition. This security flaw affects a broad range of releases including Oracle Java SE 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, and 25.0.4.1, alongside specific GraalVM versions such as 17.0.20.1, 21.0.12.1, and Enterprise Edition 21.3.19.1.1. The ImageIO library is a core part of the Java platform responsible for handling image input and output operations, making it a critical component in any application that processes visual data. Because this component interacts with external inputs to render or manipulate images, it presents a significant attack surface if not properly secured against malformed or maliciously crafted media files.
The technical nature of this vulnerability is characterized by an unauthenticated attacker gaining unauthorized read access to a subset of accessible data within the Java environment. The exploitation vector allows for network-based attacks via multiple protocols, indicating that the flaw can be triggered remotely without requiring prior authentication credentials from the victim system. Although the complexity of exploiting this vulnerability is rated as difficult, which suggests specific conditions or precise payload construction are required to trigger the memory corruption or logic error leading to information disclosure, the potential impact remains significant for targeted attacks. The attacker does not need user interaction to exploit this flaw, classifying it as a non-interactive remote code execution path that leads specifically to data exfiltration rather than full system compromise in most standard configurations.
From an operational perspective, the primary consequence of successful exploitation is unauthorized read access to sensitive information stored within the Java runtime environment or accessible by the application using ImageIO APIs. This could include cached images, temporary files, or memory contents that were not intended for public exposure. The vulnerability also poses a severe risk in environments where sandboxed applications are deployed, such as Java Web Start applications or Java applets running in browsers. In these scenarios, untrusted code loaded from the internet relies on the Java sandbox security model to restrict its privileges. If this flaw allows bypassing those restrictions through ImageIO APIs, it undermines the fundamental isolation principles of the sandbox, potentially allowing malicious scripts to read data that should remain confined within their restricted context.
This incident aligns with CWE-200, which defines Information Exposure, specifically where sensitive information is disclosed due to improper handling or processing of input data. Furthermore, in terms of adversary tactics and techniques, this vulnerability facilitates the Initial Access phase of the MITRE ATT&CK framework by allowing an attacker to gain a foothold through network-based exploitation without authentication. It may also contribute to Credential Access if the exposed data includes session tokens or other sensitive identifiers embedded within processed images. The CVSS 3.1 base score of 3.7 reflects these constraints, highlighting that while confidentiality is impacted at a low level, the high attack complexity and lack of required privileges limit the overall severity in general scenarios, though it remains critical for applications handling untrusted image inputs from external sources.
Mitigation strategies must focus on both immediate patching and architectural hardening. Organizations should immediately apply the latest security patches provided by Oracle for all affected versions listed above to close the specific code path exploited within ImageIO. For environments where upgrading is not immediately feasible, deploying a Web Application Firewall with rules capable of detecting anomalous image processing requests can provide an additional layer of defense. Additionally, developers utilizing these Java platforms should enforce strict input validation on any data passed to ImageIO APIs, ensuring that only trusted sources are processed and that file types are validated against expected MIME types before parsing. Reducing the attack surface by disabling unnecessary ImageIO plugins or restricting network access for services that do not require external image processing can further mitigate the risk of exploitation in production environments.