CVE-2018-17019 in Bro
Summary
by MITRE
In Bro through 2.5.5, there is a DoS in IRC protocol names command parsing in analyzer/protocol/irc/IRC.cc.
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Analysis
by VulDB Data Team • 05/16/2023
The vulnerability identified as CVE-2018-17019 represents a denial of service weakness affecting Bro network security monitoring software versions through 2.5.5. This issue specifically targets the IRC protocol analyzer component within Bro's framework, where improper handling of the names command during IRC protocol parsing leads to system instability. The vulnerability exists in the analyzer/protocol/irc/IRC.cc file, which processes IRC protocol traffic and handles various commands sent between IRC clients and servers. When an attacker crafts a malformed or specially constructed names command, the parser fails to properly validate or handle the input, resulting in a crash or hang of the Bro process. This represents a classic buffer over-read or improper input validation scenario that can be exploited to disrupt network monitoring operations.
The technical flaw manifests through insufficient bounds checking and input validation within the IRC protocol analyzer module. The names command in IRC protocol is used to retrieve information about users in a channel, and when Bro processes this command, it fails to properly sanitize or validate the incoming data structure. This parsing failure can cause the software to attempt to access memory locations beyond the allocated buffer boundaries or to process malformed data in an unexpected manner. The vulnerability operates at the protocol parsing layer of Bro's architecture, where network traffic is analyzed and interpreted for security monitoring purposes. According to CWE classification, this vulnerability maps to CWE-125: Out-of-bounds Read, which occurs when a program reads data past the end of a valid buffer. The issue also aligns with CWE-20: Improper Input Validation, as the system fails to properly validate incoming protocol data before processing it.
The operational impact of CVE-2018-17019 extends beyond simple service disruption to potentially compromise network monitoring capabilities. When exploited, this vulnerability can cause Bro instances to crash or become unresponsive, effectively removing network traffic analysis from the monitoring infrastructure. This creates a window of opportunity for malicious actors to conduct network activities without detection, as the security monitoring system becomes unavailable. The attack surface is particularly concerning in environments where Bro is deployed for continuous network monitoring, as a single malicious IRC packet can bring down the entire monitoring infrastructure. Organizations relying on Bro for security operations may experience significant downtime and loss of visibility into network traffic, potentially allowing attacks to go undetected for extended periods. The vulnerability can be exploited remotely through network traffic without requiring authentication or special privileges, making it particularly dangerous for publicly accessible Bro installations.
Mitigation strategies for this vulnerability should focus on immediate patching and implementing network-level controls. The primary solution involves upgrading to Bro version 2.5.6 or later, where the IRC protocol parser has been corrected to properly validate incoming names command data. Organizations should also consider implementing network segmentation and access controls to limit exposure to potentially malicious IRC traffic. Network administrators can deploy intrusion detection systems that monitor for anomalous IRC traffic patterns or implement rate limiting to prevent flood attacks that might exploit this vulnerability. From an ATT&CK framework perspective, this vulnerability relates to T1071.004: Application Layer Protocol: DNS and T1046: Network Service Scanning, as attackers may use IRC protocol analysis to identify network services or probe for vulnerabilities. Additionally, the vulnerability demonstrates the importance of input validation and proper error handling in network security tools, aligning with defensive techniques such as T1566: Credential Access and T1595: Active Scanning. Organizations should also implement proper monitoring and alerting for Bro process health to detect potential exploitation attempts and ensure rapid response to any service disruption.