CVE-2012-6700 in dhcpcd
Summary
by MITRE
The decode_search function in dhcp.c in dhcpcd 3.x does not properly free allocated memory, which allows remote DHCP servers to cause a denial of service via a crafted response.
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Analysis
by VulDB Data Team • 02/04/2019
The vulnerability identified as CVE-2012-6700 resides within the dhcpcd 3.x DHCP client implementation, specifically in the decode_search function located in dhcp.c. This flaw represents a classic memory management issue that can be exploited to disrupt network services through remote manipulation of DHCP responses. The vulnerability manifests when the DHCP client processes malformed or crafted responses from malicious DHCP servers, leading to improper memory deallocation during the search parameter decoding process. This memory handling defect creates a condition where allocated memory blocks are not properly released back to the system, resulting in gradual memory consumption that eventually leads to system resource exhaustion.
The technical exploitation of this vulnerability occurs through the manipulation of DHCP server responses that contain specially crafted search domain parameters. When the dhcpcd client receives such responses, the decode_search function fails to properly free previously allocated memory structures used for processing the search domain information. This memory leak accumulates over time as the client continues to process DHCP responses, ultimately causing the system to exhaust available memory resources and resulting in a denial of service condition. The flaw is particularly dangerous because it requires no authentication or privileged access from the attacker, making it a significant threat in network environments where DHCP servers are not properly secured or validated.
From an operational impact perspective, this vulnerability affects systems running dhcpcd 3.x versions that function as DHCP clients, particularly those in enterprise environments where automatic network configuration is relied upon. The denial of service condition can disrupt network connectivity for affected systems, potentially causing widespread disruption in network operations. The vulnerability's remote nature means that attackers can exploit it from outside the local network, making it especially concerning for systems that are not properly segmented or protected. Network administrators may observe gradual performance degradation before complete service disruption as the memory leak accumulates, complicating detection and response efforts.
The vulnerability aligns with CWE-401, which describes improper release of memory, and represents a common pattern of memory management errors that can lead to resource exhaustion attacks. This flaw can be mapped to ATT&CK technique T1499.001, which covers network denial of service attacks, and T1071.004, covering application layer protocols such as DHCP. Mitigation strategies should include immediate patching of affected dhcpcd versions to address the memory management issue in the decode_search function. Organizations should also implement network segmentation to limit DHCP server access, deploy DHCP snooping mechanisms, and establish monitoring for unusual DHCP traffic patterns that might indicate exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar memory management issues in network infrastructure components.