CVE-2020-7216 in wicked
Summary
by MITRE
An ni_dhcp4_parse_response memory leak in openSUSE wicked 0.6.55 and earlier allows network attackers to cause a denial of service by sending DHCP4 packets without a message type option.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2020-7216 represents a critical memory management flaw within the openSUSE wicked network management daemon version 0.6.55 and earlier. This issue manifests as a memory leak during the processing of DHCPv4 responses, specifically when the daemon encounters DHCP packets that lack the mandatory message type option. The vulnerability resides in the ni_dhcp4_parse_response function which fails to properly handle malformed DHCP responses, creating a condition where allocated memory is not correctly released back to the system. This memory leak occurs repeatedly with each malicious DHCP packet received, gradually consuming available system resources and ultimately leading to system instability or complete service unavailability.
The technical exploitation of this vulnerability follows a well-defined attack pattern that aligns with the ATT&CK framework's privilege escalation and denial of service tactics. Attackers can craft specially malformed DHCP packets that omit the message type option, a field that is typically required for proper DHCP communication. When the wicked daemon processes these packets through the ni_dhcp4_parse_response function, the memory leak occurs because the code path that handles missing message type options does not include proper cleanup of allocated memory structures. This behavior constitutes a classic memory leak vulnerability classified under CWE-401 as "Improper Release of Memory Before Removing Last Reference" and demonstrates poor error handling practices in network protocol parsing. The vulnerability is particularly dangerous because it requires minimal network access to exploit, as attackers only need to send malformed DHCP packets to the target system's network interface.
The operational impact of CVE-2020-7216 extends beyond simple denial of service, creating cascading effects that can compromise entire network infrastructure. When multiple malicious DHCP packets are sent to a vulnerable system, the cumulative memory consumption can cause the wicked daemon to exhaust available memory resources, leading to system crashes or forced service restarts. Network administrators may experience intermittent connectivity issues or complete network service outages, particularly in environments where automatic network configuration relies heavily on the wicked daemon. The vulnerability affects systems running openSUSE distributions that utilize wicked for DHCP management, making it relevant to enterprise network infrastructure, embedded systems, and IoT devices that depend on this network management framework. The resource exhaustion can also impact other system processes that compete for the same memory pool, potentially causing broader system instability.
Mitigation strategies for this vulnerability should address both immediate remediation and long-term architectural improvements. The most effective immediate solution involves upgrading to openSUSE wicked version 0.6.56 or later, where the memory leak has been patched through proper memory management in the ni_dhcp4_parse_response function. Network administrators should also implement DHCP filtering mechanisms at the network level to block malformed packets before they reach vulnerable systems, utilizing tools such as iptables rules or DHCP server configurations that can identify and drop packets lacking required options. Additionally, system monitoring should be enhanced to detect unusual memory consumption patterns in the wicked daemon process, enabling proactive response to potential exploitation attempts. Organizations should also consider implementing network segmentation strategies that limit direct access to systems running vulnerable versions of wicked, reducing the attack surface and providing additional defense-in-depth measures against this particular class of denial of service attacks.