CVE-2011-4868 in dhcp
Summary
by MITRE
The logging functionality in dhcpd in ISC DHCP before 4.2.3-P2, when using Dynamic DNS (DDNS) and issuing IPv6 addresses, does not properly handle the DHCPv6 lease structure, which allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via crafted packets related to a lease-status update.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability identified as CVE-2011-4868 represents a critical flaw in the Internet Systems Consortium DHCP server implementation that specifically affects the dhcpd daemon when operating in Dynamic DNS environments with IPv6 address allocation. This issue stems from improper handling of DHCPv6 lease structures within the logging subsystem, creating a pathway for remote attackers to execute denial of service attacks against network infrastructure. The vulnerability impacts ISC DHCP versions prior to 4.2.3-P2, making it a significant concern for organizations maintaining older network services that rely on dynamic IPv6 address assignment.
The technical root cause of this vulnerability lies in the insufficient validation and handling of DHCPv6 lease data structures during the logging process. When dhcpd receives crafted packets related to lease status updates in IPv6 environments with Dynamic DNS enabled, the logging function fails to properly validate the lease structure before attempting to process it. This leads to a NULL pointer dereference condition where the daemon attempts to access memory locations that have not been properly initialized or allocated, resulting in an immediate crash of the dhcpd process. The flaw specifically manifests when the logging mechanism encounters malformed or unexpected lease data that does not conform to expected DHCPv6 structures, creating a path for malicious packet crafting to trigger the vulnerability.
The operational impact of CVE-2011-4868 extends beyond simple service disruption as it can effectively take down critical network infrastructure components that depend on DHCP services for IPv6 address allocation. Network administrators responsible for maintaining IPv6-enabled networks with Dynamic DNS functionality face the risk of unauthorized denial of service attacks that can render their DHCP servers unavailable, disrupting network connectivity for all devices relying on dynamic IPv6 address assignment. This vulnerability particularly affects enterprise environments where DHCP servers are integral to network operations, potentially causing cascading failures in network services and requiring immediate remediation efforts. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring physical access or authentication credentials.
Organizations should prioritize immediate patching of affected ISC DHCP installations to address this vulnerability, as the exploitation can occur without any authentication requirements and can be executed remotely. The mitigation strategy involves upgrading to ISC DHCP version 4.2.3-P2 or later, which includes proper validation and handling of DHCPv6 lease structures within the logging functionality. Network administrators should also consider implementing additional monitoring and intrusion detection measures to identify potential exploitation attempts, as the vulnerability may be used as part of broader network reconnaissance activities. Security teams should review their network configurations to ensure that Dynamic DNS functionality is not unnecessarily enabled on DHCP servers that are exposed to untrusted networks, reducing the attack surface for this and similar vulnerabilities.
This vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions in software implementations, and represents a classic example of improper input validation leading to service disruption. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique related to network denial of service attacks, where adversaries leverage software flaws to disrupt network services. The vulnerability also demonstrates characteristics of T1595.001 which involves reconnaissance activities targeting network infrastructure, as attackers may scan for vulnerable DHCP implementations before attempting exploitation. The impact of this vulnerability underscores the importance of maintaining up-to-date network infrastructure software and implementing proper security controls to prevent unauthorized access to critical network services.