CVE-2021-42010 is a critical security vulnerability identified in Apache Heron (Incubating), an open-source distributed stream processing engine developed by the Apache Software Foundation. The vulnerability exists in versions up to and including 0.20.4-incubating and is classified as a CRLF (Carriage Return Line Feed) injection vulnerability. This flaw arises due to the lack of proper escaping of user-controllable input in log statements, allowing an attacker to inject CRLF characters into log files. Such injection can manipulate log entries, potentially enabling log forging or log injection attacks. These attacks can mislead administrators by inserting fake log entries, obfuscate malicious activities, or even facilitate further exploitation by injecting malicious content into logs that might be parsed by other systems. The vulnerability is tracked under CWE-116 (Improper Encoding or Escaping of Output) and has a CVSS v3.1 base score of 9.8, indicating a critical severity level. The vector metrics (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) highlight that the vulnerability is remotely exploitable over the network without any privileges or user interaction, and it impacts confidentiality, integrity, and availability to a high degree. The issue was addressed in Apache Heron version 0.20.5-incubating, which includes proper escaping mechanisms in log statements to prevent CRLF injection. No known exploits are currently reported in the wild, but the critical nature of the vulnerability and ease of exploitation make it a high-risk issue for affected deployments.

For European organizations utilizing Apache Heron for real-time data processing, this vulnerability poses a significant risk. Exploitation could allow attackers to inject misleading or malicious entries into system logs, undermining the integrity and reliability of audit trails and monitoring systems. This can hinder incident detection and response efforts, potentially allowing attackers to maintain persistence or cover tracks. Given the critical CVSS score, attackers could also impact system availability or exfiltrate sensitive information by leveraging the vulnerability in combination with other attack vectors. Organizations in sectors such as finance, telecommunications, energy, and critical infrastructure—where Apache Heron might be deployed for streaming analytics—could face operational disruptions and compliance issues, especially under stringent European data protection regulations like GDPR. The ability to exploit this vulnerability remotely without authentication further elevates the threat, making it imperative for European entities to prioritize remediation to avoid potential data breaches, service outages, or reputational damage.

European organizations should immediately upgrade Apache Heron to version 0.20.5-incubating or later, where the CRLF injection vulnerability has been fixed. Beyond patching, organizations should implement strict input validation and sanitization on any data that is logged, ensuring that control characters such as CR and LF are properly escaped or removed before logging. Employ centralized log management solutions with anomaly detection capabilities to identify suspicious log entries indicative of injection attempts. Regularly audit and monitor logs for inconsistencies or unexpected entries. Additionally, restrict network access to Apache Heron management interfaces and streaming endpoints using firewalls and network segmentation to reduce exposure. Implement role-based access controls and ensure that only authorized personnel can modify logging configurations or access logs. Finally, maintain an up-to-date inventory of Apache Heron deployments across the organization to ensure all instances are identified and patched promptly.