CVE-2018-16807 in Bro
Summary
by MITRE
In Bro through 2.5.5, there is a memory leak potentially leading to DoS in scripts/base/protocols/krb/main.bro in the Kerberos protocol parser.
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Analysis
by VulDB Data Team • 09/04/2025
The vulnerability identified as CVE-2018-16807 affects the Bro network security monitoring system version 2.5.5 and earlier, specifically within the Kerberos protocol parser component. This memory leak occurs in the script located at scripts/base/protocols/krb/main.bro, representing a critical weakness in the system's ability to handle Kerberos authentication traffic. The flaw manifests as an incremental memory consumption pattern that can eventually lead to system resource exhaustion and denial of service conditions. Bro, which is widely deployed in network security operations for protocol analysis and intrusion detection, becomes vulnerable to this issue when processing Kerberos protocol messages, particularly during authentication exchanges.
The technical root cause of this vulnerability lies in improper memory management within the Kerberos protocol parser implementation. When Bro processes Kerberos packets, the memory allocated for parsing and storing Kerberos message data is not consistently released or properly managed, leading to gradual memory accumulation over time. This memory leak is particularly concerning because Kerberos is a widely used authentication protocol in enterprise environments, making the affected Bro installations susceptible to sustained resource exhaustion attacks. The vulnerability operates at the application layer, specifically targeting the protocol parsing logic that handles Kerberos authentication mechanisms, and can be triggered through normal network traffic containing Kerberos messages.
The operational impact of CVE-2018-16807 extends beyond simple resource consumption, as it can effectively disable network monitoring capabilities for affected systems. When the memory leak reaches critical thresholds, Bro instances may crash or become unresponsive, disrupting security monitoring operations and potentially leaving network traffic unmonitored during critical periods. This vulnerability particularly affects organizations relying on Bro for security operations, as it can be exploited by adversaries who send crafted Kerberos traffic to consume system resources gradually. The DoS condition can persist until manual intervention occurs to restart the Bro service or the system is rebooted, creating potential windows for additional attacks or security gaps during service restoration.
Organizations should implement immediate mitigations including upgrading to Bro version 2.5.6 or later where this vulnerability has been patched, as well as implementing network monitoring to detect unusual memory consumption patterns in Bro instances. Network administrators should also consider implementing rate limiting or traffic filtering for Kerberos protocol traffic when possible, and establish monitoring alerts for memory usage thresholds. The vulnerability aligns with CWE-401, which specifically addresses memory leaks in software systems, and represents a classic example of how protocol parsing components can introduce stability risks in network security tools. From an ATT&CK perspective, this vulnerability could be leveraged as part of a broader attack strategy to disrupt security operations and maintain persistence within targeted networks, making it a significant concern for defensive operations and incident response teams.