CVE-2026-112331 in Motor.NET
Summary
by MITRE • 10/22/2026
Motor.NET before 0.19.0 contains a denial-of-service vulnerability that allows a remote attacker who can produce records to a consumed topic to crash the service permanently by sending a single crafted record. By setting the content-type header to application/cloudevents+json and omitting required CloudEvent attributes (id, source, type), the attacker triggers an ArgumentException in KafkaMessageConsumer.SingleMessageHandlingAsync that is treated as fatal, causing the host to stop and re-process the same poison record on every restart, resulting in a permanent crash-loop.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified in Motor.NET prior to version 0.19.0 represents a critical denial-of-service flaw rooted in insufficient input validation within the Kafka message consumption pipeline. This issue specifically affects systems utilizing the Motor.NET library for integrating with Apache Kafka, allowing any remote attacker who possesses write access to a consumed topic to disrupt service availability permanently. The core technical failure lies in the handling of CloudEvents formatted messages where the content-type header is explicitly set to application/cloudevents+json but essential attributes such as id, source, and type are omitted from the payload. This malformed input triggers an unhandled ArgumentException within the KafkaMessageConsumer.SingleMessageHandlingAsync method. Because this exception is not caught by a local error handler or retry mechanism, it propagates up the call stack and is interpreted by the host application as a fatal failure condition rather than a recoverable processing error.
The operational impact of this vulnerability extends beyond a simple transient service interruption due to the specific behavior of the underlying message broker integration logic. When the ArgumentException occurs, the current process terminates abruptly. However, because the poison record remains in the topic and is typically retried or re-consumed upon restart depending on consumer group configuration, the application enters an infinite crash loop. Each time the service attempts to recover by restarting, it immediately encounters the same malformed record, triggers the identical exception, and crashes again. This cycle prevents any legitimate traffic from being processed effectively and consumes system resources through continuous process churn, leading to a permanent denial of service for all consumers relying on that topic until manual intervention occurs or the poison message is removed.
From a security architecture perspective, this flaw aligns with CWE-20 Improper Input Validation, as the application fails to verify that required fields are present before attempting to deserialize and process the CloudEvent object. It also reflects CWE-755: Improper Handling of Exceptional Conditions, where exceptional states resulting from invalid input lead to uncontrolled termination rather than graceful degradation or error reporting. In terms of attack vectors, this vulnerability can be mapped to MITRE ATT&CK technique T1499 Endpoint Denial of Service, specifically under the sub-category of resource exhaustion through application crashes. The attacker does not need complex exploitation chains; a single crafted HTTP-like message structure within the Kafka payload is sufficient to achieve persistent disruption.
Mitigation strategies must focus on both immediate remediation and long-term defensive coding practices. The primary solution is to upgrade Motor.NET to version 0.19.0 or later, where this specific handling logic has been corrected to either validate inputs prior to processing or catch the resulting exceptions without treating them as fatal host-level errors. For environments unable to patch immediately, operational mitigations include implementing strict schema validation at the Kafka producer level to ensure all CloudEvent attributes are present before messages enter the topic. Additionally, configuring consumer groups with appropriate retry policies and dead-letter queue mechanisms can prevent poison records from causing infinite loops. Monitoring solutions should be tuned to detect rapid service restarts associated with specific topics as an indicator of this exploitation attempt, allowing for automated isolation or alerting before total service collapse occurs.