CVE-2026-91409 in Java SE
Summary
by MITRE • 10/21/2026
Vulnerability in Oracle Java SE (component: Networking). The supported version that is affected is Oracle Java SE: 27. Difficult to exploit vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE. Successful attacks of this vulnerability can result in unauthorized ability to cause a partial denial of service (partial DOS) of Oracle Java SE. 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 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the Networking component of Oracle Java SE version 27, representing a significant security concern for environments relying on this specific release. The core technical flaw allows an unauthenticated attacker to exploit the system through network access using multiple protocols. This indicates that the weakness is not confined to a single communication channel but permeates various networking interfaces exposed by the Java runtime environment. The difficulty of exploitation is classified as high, suggesting that while the vulnerability exists and can be triggered remotely without prior authentication, it requires specific conditions or precise triggering mechanisms rather than being trivially exploitable via automated tools alone. This characteristic often implies a race condition, memory corruption issue under specific state transitions, or logic error in protocol handling that demands careful orchestration by an attacker to succeed consistently.
The operational impact of this vulnerability is primarily centered on availability, as evidenced by the CVSS 3.1 base score of 3.7 which focuses exclusively on Availability impacts with no consequences for Confidentiality or Integrity. Successful exploitation results in a partial denial of service against Oracle Java SE itself. This means that an attacker can degrade the performance or responsiveness of the Java runtime environment, potentially causing threads to hang, resources to leak, or processes to become unresponsive without necessarily crashing the entire system immediately. For organizations running critical business logic within this version, such degradation can lead to significant operational disruptions, delayed transaction processing, and reduced user experience for applications dependent on stable network connectivity through Java-based services.
The attack vector is particularly relevant in contexts where APIs are utilized, especially those involved in web services that supply data directly to the affected components. This suggests that maliciously crafted inputs or malformed packets sent via these API endpoints can trigger the underlying flaw. Furthermore, this vulnerability extends its threat surface to typical Java deployments involving clients running sandboxed applications such as Java Web Start apps or applets. These environments rely heavily on the Java security manager and sandboxing mechanisms to isolate untrusted code from the host system. When an application loads and executes code originating from external sources like the internet, it assumes that the underlying runtime is secure against network-level attacks. The presence of this vulnerability undermines that assumption, as a successful exploit could bypass or overwhelm the sandbox's protective boundaries by exhausting resources at the networking layer before higher-level security checks can effectively mitigate the damage.
From an industry standards perspective, this vulnerability aligns with CWE-400: Uncontrolled Resource Consumption, which describes scenarios where a software product does not properly control the allocation and maintenance of a limited resource, thereby enabling an attacker to make that resource unavailable or consume excessive amounts of it. Additionally, in terms of tactical mapping within the MITRE ATT&CK framework, this behavior corresponds to T1499: Endpoint Denial of Service, specifically under techniques designed to exhaust system resources such as CPU, memory, or network bandwidth to disrupt service availability. The high attack complexity and lack of required user interaction place it firmly in the remote exploitation category, requiring careful consideration during threat modeling for any Java-based infrastructure exposed to untrusted networks.
Mitigation strategies must prioritize immediate patching if feasible, given that Oracle Java SE 27 is a specific version where this flaw exists. Organizations should evaluate their exposure by identifying all instances of Java Web Start applications and applets that load external code, as these are the most likely vectors for exploitation due to their reliance on network connectivity with untrusted sources. If patching is not immediately possible, implementing strict network segmentation rules can help mitigate risk by restricting access to the affected components from untrusted networks. Additionally, deploying intrusion detection systems configured to detect anomalous patterns of resource consumption or malformed packets associated with the specific protocols exploited in this vulnerability can provide an additional layer of defense. Regular auditing of Java deployment configurations and disabling unnecessary networking features within the sandboxed environments will further reduce the attack surface available to potential adversaries seeking to cause denial-of-service conditions.