CVE-2015-8605 in DHCPD
Summary
by MITRE
ISC DHCP 4.x before 4.1-ESV-R12-P1 and 4.2.x and 4.3.x before 4.3.3-P1 allows remote attackers to cause a denial of service (application crash) via an invalid length field in a UDP IPv4 packet.
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Analysis
by VulDB Data Team • 05/05/2019
The vulnerability identified as CVE-2015-8605 affects ISC DHCP server versions prior to specific patches, representing a critical denial of service weakness that can be exploited remotely. This issue resides within the DHCP server's packet processing logic where it fails to properly validate the length field of incoming UDP IPv4 packets. The flaw enables attackers to craft malicious packets with invalid length values that, when processed by the vulnerable DHCP server, trigger application crashes and subsequent service disruption. The vulnerability specifically impacts versions 4.1.x before 4.1-ESV-R12-P1 and 4.2.x series as well as 4.3.x versions before 4.3.3-P1, indicating a widespread issue affecting multiple release branches of the ISC DHCP software.
The technical implementation of this vulnerability stems from insufficient input validation within the DHCP server's network packet handling routines. When the server receives a UDP packet containing an invalid length field, the parsing logic does not properly sanitize or reject malformed data before attempting to process the packet contents. This lack of proper boundary checking creates a condition where the application's memory management routines encounter unexpected data structures, leading to memory corruption and ultimately application termination. The flaw operates at the network protocol layer where UDP packets are received and processed, making it particularly dangerous as it can be exploited without authentication or privileged access. The vulnerability is classified under CWE-129 as an improper input validation issue, specifically involving the handling of invalid length parameters in network protocols.
The operational impact of CVE-2015-8605 extends beyond simple service interruption, as it can be leveraged to create persistent denial of service conditions within network infrastructure. Organizations relying on ISC DHCP servers for IP address allocation and network configuration management face significant risk when exposed to this vulnerability, as attackers can repeatedly exploit it to maintain service disruption. The attack vector requires only network access to the affected DHCP server, making it particularly dangerous in environments where DHCP servers are accessible to untrusted network segments. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries exploit weaknesses in network services to disrupt availability. The impact is particularly severe in enterprise environments where DHCP servers serve as critical infrastructure components for network operations, potentially affecting thousands of devices simultaneously if the attack is successful.
Mitigation strategies for CVE-2015-8605 primarily involve applying the vendor-provided patches and updates that address the input validation flaw in ISC DHCP server implementations. Organizations should immediately upgrade to patched versions 4.1-ESV-R12-P1, 4.3.3-P1, or later releases that contain proper validation of UDP packet length fields. Network segmentation and access control measures can provide additional defense in depth by limiting direct network access to DHCP servers from untrusted networks. Implementing network monitoring solutions that can detect anomalous packet patterns or unusual DHCP traffic may help identify exploitation attempts. Security teams should also consider deploying intrusion detection systems configured to alert on malformed DHCP packets that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in network services and reinforces the need for regular security updates and patch management processes. Organizations should also implement network access controls that restrict direct access to DHCP servers and consider deploying DHCP servers in protected network segments with appropriate firewall rules to minimize exposure to potential attackers.