CVE-2011-2749 in DHCP
Summary
by MITRE
The server in ISC DHCP 3.x and 4.x before 4.2.2, 3.1-ESV before 3.1-ESV-R3, and 4.1-ESV before 4.1-ESV-R3 allows remote attackers to cause a denial of service (daemon exit) via a crafted BOOTP packet.
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Analysis
by VulDB Data Team • 11/12/2024
The vulnerability identified as CVE-2011-2749 represents a critical denial of service flaw within the Internet Systems Consortium DHCP implementations. This vulnerability affects ISC DHCP server versions across multiple release streams including 3.x and 4.x series, with specific unaffected versions noted as 4.2.2 and later releases in the 3.1-ESV and 4.1-ESV branches. The flaw manifests when the DHCP daemon processes malformed BOOTP packets, leading to daemon termination and subsequent service disruption for network clients seeking IP address allocation. This vulnerability directly impacts network infrastructure reliability and can be exploited by remote attackers without authentication requirements.
The technical mechanism behind this vulnerability involves improper input validation within the DHCP server's packet processing routine. When the server receives a crafted BOOTP packet containing malformed or unexpected data structures, the parsing logic fails to properly handle the edge case conditions, resulting in an unhandled exception or memory corruption that causes the daemon process to exit abruptly. This behavior aligns with CWE-129, which describes issues related to improper validation of input boundaries, and specifically relates to improper handling of malformed network packets in server applications. The vulnerability demonstrates a classic buffer over-read or parsing error that occurs during the BOOTP packet interpretation phase, where the server fails to implement adequate defensive programming practices.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and client connectivity. In enterprise environments where DHCP serves as a critical infrastructure component for IP address allocation, a successful exploitation could result in widespread network outages affecting multiple clients simultaneously. Network administrators would experience service interruptions that could last until manual intervention occurs to restart the DHCP daemon or implement temporary workarounds. The vulnerability's remote exploitability means that attackers can trigger the denial of service from outside the network perimeter, making it particularly dangerous for exposed DHCP servers. This scenario directly maps to ATT&CK technique T1499.004, which describes network denial of service attacks targeting infrastructure services.
Mitigation strategies for CVE-2011-2749 primarily involve immediate deployment of patched versions from ISC, specifically upgrading to versions 4.2.2 or later for the 4.x series and 3.1-ESV-R3 or later for the 3.1-ESV branch. Organizations should also implement network segmentation to limit exposure of DHCP servers to untrusted networks and deploy intrusion detection systems that can identify and alert on malformed BOOTP packet patterns. Additional defensive measures include configuring DHCP servers with appropriate access controls and implementing monitoring solutions that can detect daemon termination events. The vulnerability highlights the importance of input validation and defensive programming practices in network infrastructure software, emphasizing that even seemingly benign protocols like BOOTP require robust error handling mechanisms to prevent exploitation. Organizations should also consider implementing redundant DHCP services and failover mechanisms to minimize the impact of such vulnerabilities on overall network availability.