CVE-2022-2929 in DHCP
Summary
by MITRE • 10/07/2022
In ISC DHCP 1.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1 a system with access to a DHCP server, sending DHCP packets crafted to include fqdn labels longer than 63 bytes, could eventually cause the server to run out of memory.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/15/2024
The vulnerability identified as CVE-2022-2929 represents a critical memory exhaustion flaw within ISC DHCP server implementations spanning versions 1.0 through 4.4.3 and specifically affecting the 4.1-ESV-R1 through 4.1-ESV-R16-P1 release series. This issue stems from inadequate input validation mechanisms within the DHCP server's handling of Fully Qualified Domain Name (FQDN) labels contained in DHCP packets. The vulnerability operates by exploiting the server's failure to properly enforce length constraints on FQDN labels, allowing malicious actors to craft DHCP packets with labels exceeding the standard 63-byte limit imposed by DNS specifications. This flaw falls under the CWE-122 weakness category, which encompasses buffer overflow conditions that can lead to memory corruption and system instability. The attack vector requires only network access to the target DHCP server, making it particularly dangerous in environments where DHCP servers are exposed to untrusted networks or where attackers can inject malicious DHCP packets through network infiltration.
The technical execution of this vulnerability involves sending specially crafted DHCP packets containing FQDN labels that exceed the 63-byte DNS label limit. When the ISC DHCP server processes these malformed packets, it attempts to allocate memory to store the excessively long labels without proper bounds checking. This leads to progressive memory consumption as the server repeatedly processes these malformed packets, eventually exhausting available memory resources and causing the DHCP service to become unresponsive or crash entirely. The memory exhaustion occurs through the server's internal data structures that maintain FQDN information for lease management and DNS update operations, where each oversized label consumes additional memory proportional to its length. This behavior aligns with the ATT&CK technique T1499.001, which covers network denial of service attacks, specifically targeting resource exhaustion through malformed packet processing. The vulnerability demonstrates a classic example of how insufficient input validation can lead to resource exhaustion attacks, where the attacker leverages the server's legitimate processing functions to consume system resources.
The operational impact of CVE-2022-2929 extends beyond simple service disruption, potentially compromising network infrastructure availability and reliability. When a DHCP server becomes unresponsive due to memory exhaustion, network clients lose the ability to obtain IP addresses dynamically, leading to complete network connectivity failures for affected devices. This vulnerability particularly affects enterprise networks where DHCP servers serve as critical infrastructure components managing IP address allocation across large networks. The attack can be executed with minimal resources and technical expertise, making it attractive to threat actors seeking to disrupt network operations. Organizations running affected ISC DHCP server versions face significant risk of service degradation or complete outages, especially in environments with high DHCP traffic volumes where the memory exhaustion can occur rapidly. The vulnerability also impacts the server's ability to maintain accurate DNS records and lease information, potentially leading to long-term network configuration issues and increased administrative overhead for recovery operations. Security professionals should consider this vulnerability as part of broader network denial of service strategies and implement appropriate monitoring to detect unusual memory consumption patterns in DHCP server environments.
Mitigation strategies for CVE-2022-2929 focus on both immediate patching and operational controls to prevent exploitation. The primary recommendation involves upgrading affected ISC DHCP server installations to versions that include proper input validation for FQDN labels, typically those released after the vulnerability disclosure. Organizations should implement network segmentation and access controls to limit direct access to DHCP servers from untrusted networks, reducing the attack surface for this vulnerability. Network monitoring solutions should be configured to detect unusual DHCP packet patterns and memory consumption spikes that may indicate exploitation attempts. The implementation of DHCP snooping and other network security measures can help filter out malformed DHCP packets before they reach the server. Additionally, administrators should consider implementing rate limiting and connection pooling mechanisms to prevent rapid memory exhaustion through repeated packet processing. Regular security assessments and vulnerability scanning should include checks for affected ISC DHCP server versions to ensure comprehensive protection. The vulnerability highlights the importance of proper input validation and resource management in network infrastructure components, emphasizing that even well-established software can contain critical flaws when processing untrusted network data. Organizations should also establish incident response procedures specifically addressing DHCP server resource exhaustion scenarios to minimize downtime and recovery times when such attacks occur.