CVE-2026-9338 in WebSphere Application Server
Summary
by MITRE • 09/10/2026
IBM WebSphere Application Server 9.0, and 8.5 is vulnerable to a denial of service, caused by sending a specially-crafted request. A remote attacker could exploit this vulnerability to trigger excessive resource consumption, potentially leading to reduced availability of the affected service.
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Analysis
by VulDB Data Team • 09/10/2026
The IBM WebSphere Application Server versions 9.0 and 8.5 are susceptible to a denial of service vulnerability that stems from improper handling of specific HTTP requests. This flaw allows a remote attacker who can interact with the application server's network interface to trigger excessive resource consumption within the system. The core technical issue involves the server failing to adequately validate or limit the complexity, size, or processing requirements of incoming request payloads before they are processed by internal components. When an attacker sends a specially crafted request designed to exploit this logic error, it forces the application server into an inefficient execution path that consumes disproportionate amounts of CPU cycles and memory resources relative to the input provided.
This vulnerability is classified under CWE-400, which denotes uncontrolled resource consumption, as well as CWE-20, improper input validation. From a tactical perspective, this aligns with MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically where an attacker uses application layer attacks to exhaust system resources rather than relying on network-level flooding. The operational impact is significant because the excessive resource consumption can lead to service degradation or complete unavailability for legitimate users. In a production environment, this could result in extended downtime, loss of business continuity, and increased operational costs due to the need for manual intervention to restart services or scale infrastructure temporarily to mitigate the load caused by malicious traffic.
The attack vector is remote, meaning that an adversary does not require prior authentication or access to the underlying operating system if they can reach the application server over the network. This makes the vulnerability particularly dangerous in internet-facing deployments where WebSphere Application Server instances are exposed directly to untrusted networks. The ability to trigger this condition with a single crafted request lowers the barrier for exploitation, allowing even low-skilled attackers to disrupt service availability without needing complex multi-stage exploit chains or persistent access credentials.
Mitigation strategies should focus on immediate patching and network-level defenses. IBM has released updates that address these specific flaws in newer versions of WebSphere Application Server 9.0 and 8.5; therefore, applying the latest cumulative fixes is the primary remediation step. In addition to software updates, organizations should implement web application firewalls or reverse proxies capable of inspecting incoming traffic for anomalous patterns indicative of resource exhaustion attacks. Rate limiting and request size restrictions can also help mitigate the impact by preventing any single client from overwhelming server resources with excessively large or complex payloads. Regular security audits and penetration testing focused on input validation logic are recommended to identify similar weaknesses in custom applications deployed on this platform.