CVE-2026-76401 in Connect for Kafka
Summary
by MITRE • 08/20/2026
In Splunk Connect for Kafka versions below 2.2.7, an unauthenticated user who can reach the Kafka Connect Representational State Transfer (REST) API could configure timestamp extraction with a crafted regular expression and matching event data to block a Kafka Connect worker thread, stopping event delivery for the affected connector. The vulnerability is possible because timestamp extraction evaluates customer-supplied regular expressions without a time limit. For more information see Install Splunk Connect for Kafka (https://help.splunk.com/en/data-management/integrate-data-with-add-ons/splunk-connect-for-kafka/2.2/install/install-splunk-connect-for-kafka) and Data ingestion parameters for Splunk Connect for Kafka (https://help.splunk.com/en/data-management/integrate-data-with-add-ons/splunk-connect-for-kafka/2.2/overview/data-ingestion-parameters-for-splunk-connect-for-kafka) in the Splunk documentation.
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Analysis
by VulDB Data Team • 08/20/2026
Splunk Connect for Kafka versions prior to 2.2.7 contain a critical denial of service vulnerability within its timestamp extraction mechanism, which allows an unauthenticated attacker who has network access to the Kafka Connect REST API to disrupt data ingestion services. This flaw stems from the system's handling of regular expressions provided by users during configuration without implementing any execution time limits or complexity constraints. When a user submits a crafted regular expression designed to trigger catastrophic backtracking against specific event data, the underlying Java Virtual Machine thread responsible for processing that connector becomes blocked indefinitely. Because Kafka Connect relies on these worker threads to poll and process messages from topics, blocking a single thread can effectively halt event delivery for the entire affected connector, leading to significant operational disruptions in downstream analytics pipelines.
The technical root cause of this vulnerability lies in the lack of input validation regarding regex complexity during the timestamp extraction phase. Regular expressions are powerful tools for pattern matching but are susceptible to ReDoS attacks when they contain ambiguous quantifiers or nested loops that can result in exponential time complexity relative to the length of the input string. In this specific implementation, Splunk Connect for Kafka evaluates customer-supplied regular expressions without a timeout mechanism to abort execution if processing exceeds a safe threshold. Consequently, an attacker who can reach the REST API endpoint does not need valid credentials or high-level privileges; they only require network connectivity to submit configuration changes that include malicious regex patterns paired with matching payload data. This design oversight transforms a standard administrative feature into a vector for service disruption.
From an operational perspective, the impact of this vulnerability is severe as it directly compromises the availability component of the CIA triad. Kafka Connect serves as a critical bridge between Apache Kafka and various external systems or storage backends, including Splunk Enterprise. When worker threads are blocked by malicious regex execution, new events cease to be ingested into the target system. This results in gaps in logging data, which can hinder security monitoring capabilities, delay incident response efforts, and violate service level agreements related to data freshness. Since Kafka Connect often runs as a long-lived process with limited automatic recovery mechanisms for hung threads, manual intervention is typically required to restart the connector or worker nodes, further extending downtime and increasing operational overhead for administrators.
To mitigate this risk, organizations running Splunk Connect for Kafka versions below 2.2.7 must upgrade immediately to version 2.2.7 or later, where the vendor has addressed the regex evaluation logic by implementing appropriate safeguards against catastrophic backtracking. Until an upgrade is feasible, administrators should restrict network access to the Kafka Connect REST API using firewalls or authentication proxies to ensure that only trusted internal services can submit configuration changes. Additionally, it is advisable to audit existing connector configurations for complex regular expressions and replace them with simpler patterns where possible. Monitoring system resources such as CPU usage on worker nodes may also help detect ongoing exploitation attempts characterized by sustained high processor load without corresponding data throughput.
This vulnerability aligns with CWE-400, which describes uncontrolled resource consumption leading to denial of service conditions. It is further categorized under the Common Weakness Enumeration standard for regular expression issues that allow attackers to cause performance degradation through crafted inputs. In terms of offensive security frameworks, this exploit technique corresponds to ATT&CK tactic T1499, specifically endpoint or application exhaustion via resource starvation methods like ReDoS attacks. Understanding these classifications helps in mapping defensive controls and detection rules within broader enterprise security architectures to identify similar patterns in other applications that may lack robust input validation for regex processing engines.