CVE-2026-78543 in App Connect Enterprise
Summary
by MITRE • 09/04/2026
IBM App Connect Enterprise 13.0.1.0 through 13.0.8.1, and 12.0.1.0 through 12.0.12.28 and IBM Integration Bus for z/OS 10.1.0.0 through 10.1.0.7 could allow a remote attacker to cause a denial of service due to an infinite loop.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in IBM App Connect Enterprise versions ranging from 13.0.1.0 through 13.0.8.1, as well as version 12.0.1.0 through 12.0.12.28, and the corresponding legacy IBM Integration Bus for z/OS versions 10.1.0.0 through 10.1.0.7, represents a significant availability risk due to its potential for remote exploitation leading to service disruption. This flaw is fundamentally characterized by an infinite loop condition that can be triggered by external actors without requiring authentication in many deployment scenarios. The presence of such a logic error within the core message processing engine or protocol handlers allows an attacker to consume critical system resources, specifically CPU cycles and memory allocation associated with thread management, thereby degrading the performance of the integration platform for all users sharing those resources.
From a technical perspective, this vulnerability aligns closely with Common Weakness Enumeration identifier CWE-835, which describes loops that do not terminate or take an excessively long time to complete. In the context of enterprise service bus and message broker architectures like IBM App Connect Enterprise, these components are designed to handle high volumes of concurrent messages across various protocols including HTTP, MQ, FTP, and others. When a malformed request or specifically crafted payload is processed by the affected versions, it triggers an internal logic path that fails to meet its termination condition. This results in a thread becoming permanently stuck in execution mode, effectively hanging the processing unit responsible for handling incoming connections. Since integration platforms often rely on fixed-size thread pools to manage concurrency, the exhaustion of these threads due to multiple instances of this infinite loop can lead to a complete inability to process new legitimate requests.
The operational impact of this denial-of-service condition is severe for organizations relying on IBM App Connect Enterprise or Integration Bus as critical middleware infrastructure. In production environments where high availability and low latency are paramount, the degradation caused by resource exhaustion can result in significant business interruptions. Downstream systems that depend on real-time data exchange through these integration points may experience timeouts, failed transactions, or cascading failures if they do not have adequate circuit breakers or fallback mechanisms configured. Furthermore, because this vulnerability allows for remote triggering, it poses a threat to any system exposed to untrusted networks unless strictly firewalled and isolated behind robust perimeter defenses that inspect traffic deeply enough to detect the specific patterns causing the loop.
This type of availability-focused attack is often categorized under MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically within the context of resource exhaustion via application layer attacks. Attackers may leverage automated tools to send a high volume of crafted requests targeting the vulnerable endpoints, aiming to saturate the server's capacity more rapidly than it can recover or restart affected threads. The persistence of this issue across multiple major version lines indicates that while some remediation efforts were applied in later patches, earlier versions and specific configuration paths remained susceptible until the respective fix levels were deployed.
Mitigation strategies must prioritize immediate patching to the latest fixed versions provided by IBM for each supported release line. For organizations unable to immediately upgrade due to compatibility constraints or testing requirements, network-level controls should be implemented to restrict access to the integration platform interfaces from untrusted sources. Implementing rate limiting and request validation at the load balancer or web application firewall level can help mitigate the impact of volumetric attacks exploiting this flaw. Additionally, monitoring solutions should be configured to detect abnormal spikes in CPU usage or thread count associated with specific service endpoints, allowing for rapid identification and isolation of affected nodes before total system failure occurs. Regular security assessments and penetration testing focused on availability constraints are recommended to ensure that such logic errors do not persist in customized integrations or extended configurations built upon the base platform.