CVE-2026-83276 in Helidon
Summary
by MITRE • 09/16/2026
Vulnerability in the Helidon product of Oracle Fusion Middleware (component: helidon-webclient-http2). Supported versions that are affected are 4.0.0-4.5.4. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP/2 to compromise Helidon. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of Helidon. CVSS 3.1 Base Score 7.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
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Analysis
by VulDB Data Team • 09/16/2026
The identified vulnerability resides within the helidon-webclient-http2 component of Oracle Fusion Middleware's Helidon product line, specifically affecting versions ranging from 4.0.0 through 4.5.4. This security flaw is classified as a high-severity availability issue with a CVSS v3.1 base score of 7.5. The vulnerability stems from an implementation error in the HTTP/2 protocol handling logic within the web client module, which fails to properly manage certain malformed or edge-case requests sent over network connections. Because the flaw is easily exploitable and requires no authentication, it presents a significant risk to any system running these affected versions that exposes this component to external networks. The primary operational impact of this vulnerability is a denial-of-service condition, manifesting as either a complete hang or a frequently repeatable crash of the Helidon service. This effectively renders the application unavailable to legitimate users and can disrupt downstream services dependent on it.
From a technical perspective, the root cause aligns with CWE-20 Improper Input Validation, where the input data received via HTTP/2 is not sufficiently sanitized or validated before processing. The attacker leverages this weakness by sending specific crafted requests that trigger an internal state inconsistency or resource exhaustion within the Helidon runtime environment. This behavior maps directly to MITRE ATT&CK technique T1499 Endpoint Denial of Service, specifically under the sub-technique for application-level flooding or logic exploitation. Unlike volumetric attacks that rely on bandwidth saturation, this vulnerability exploits logical flaws in the protocol implementation, allowing a single attacker with minimal resources to disrupt service continuity. The lack of authentication requirements means that any entity capable of reaching the network interface hosting Helidon can initiate an attack, significantly expanding the potential threat surface beyond internal networks to public-facing internet endpoints if not properly firewalled or rate-limited.
The consequences of successful exploitation are severe for organizations relying on Helidon for microservices architecture due to its impact on availability metrics and service level agreements. A complete crash requires manual intervention or automated restart mechanisms, leading to downtime that can affect business operations, user experience, and data integrity if transactions were in progress during the outage. Furthermore, repeated crashes may indicate instability in the underlying infrastructure, potentially masking other security issues or causing cascading failures across interconnected services in a distributed system environment. To mitigate this risk, organizations must immediately apply the latest patches provided by Oracle for Helidon versions 4.0.0 through 4.5.4. If patching is not immediately feasible, deploying network-level controls such as Web Application Firewalls with specific rules to detect and block anomalous HTTP/2 traffic patterns can provide a temporary layer of defense. Additionally, implementing strict rate limiting on incoming connections and ensuring that Helidon instances are placed behind robust load balancers capable of detecting and dropping malicious requests before they reach the application logic will help reduce exposure until permanent remediation is applied. Regular security assessments and penetration testing focused on HTTP/2 implementation flaws should also be conducted to identify similar vulnerabilities in other components of the middleware stack.