CVE-2015-8373 in Kea
Summary
by MITRE
The kea-dhcp4 and kea-dhcp6 servers 0.9.2 and 1.0.0-beta in ISC Kea, when certain debugging settings are used, allow remote attackers to cause a denial of service (daemon crash) via a malformed packet.
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Analysis
by VulDB Data Team • 07/01/2022
The CVE-2015-8373 vulnerability affects the ISC Kea DHCP servers version 0.9.2 and 1.0.0-beta, specifically when certain debugging configurations are enabled. This vulnerability represents a denial of service condition that can be triggered remotely through the careful construction of malformed network packets. The issue stems from insufficient input validation within the DHCP packet processing logic of the kea-dhcp4 and kea-dhcp6 server implementations, which fail to properly handle malformed or unexpected packet structures during debugging operations. When these servers encounter crafted packets under debugging conditions, the malformed data causes the daemon process to crash and terminate unexpectedly, resulting in complete service disruption for affected networks.
The technical flaw manifests in the server's debugging code path where packet validation routines are bypassed or inadequately implemented. According to CWE classification, this vulnerability aligns with CWE-129 Input Validation and Output Encoding, specifically addressing weak input validation that allows malformed data to propagate through the system. The vulnerability exists because the debugging features, which are intended for development and troubleshooting purposes, do not properly sanitize incoming packet data before processing. This creates a scenario where remote attackers can craft specially formatted DHCP packets that, when processed by the server in debug mode, trigger memory corruption or invalid memory access conditions leading to process termination. The attack vector is particularly concerning because it requires no authentication or privileged access, making it a straightforward remote denial of service threat.
The operational impact of CVE-2015-8373 extends beyond simple service disruption, as it can effectively take down critical network infrastructure components that rely on DHCP services for device provisioning and network connectivity. Network administrators using ISC Kea servers in production environments with debugging enabled are particularly vulnerable, as the crash condition can occur at any time without warning. This vulnerability directly impacts network availability and can cause cascading failures in environments where DHCP services are integral to network operations, potentially affecting hundreds or thousands of devices simultaneously. The vulnerability also exposes potential attack surfaces that could be leveraged in combination with other exploits, as the server crash may provide opportunities for further reconnaissance or additional attack vectors.
Mitigation strategies for CVE-2015-8373 primarily focus on disabling debugging features in production environments and implementing proper input validation controls. Organizations should immediately disable debugging settings on all production ISC Kea DHCP servers and ensure that these configurations are not enabled in any environment where the servers are exposed to untrusted network traffic. The recommended approach includes applying the vendor-provided patches or upgrading to versions that have addressed this vulnerability, as the issue was resolved in subsequent releases of the ISC Kea software. Network segmentation and access controls should be implemented to limit exposure of DHCP servers to untrusted networks, while monitoring systems should be configured to detect and alert on unusual daemon crash patterns. From an ATT&CK perspective, this vulnerability maps to T1499.004 Network Denial of Service and T1071.004 Application Layer Protocol, as it exploits network protocols and causes service disruption through malformed packet delivery. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of debugging configurations that could expose the system to similar risks.