CVE-2011-2716 in BusyBox
Summary
by MITRE
The DHCP client (udhcpc) in BusyBox before 1.20.0 allows remote DHCP servers to execute arbitrary commands via shell metacharacters in the (1) HOST_NAME, (2) DOMAIN_NAME, (3) NIS_DOMAIN, and (4) TFTP_SERVER_NAME host name options.
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Analysis
by VulDB Data Team • 12/05/2021
The vulnerability identified as CVE-2011-2716 represents a critical command injection flaw in the udhcpc DHCP client component of BusyBox versions prior to 1.20.0. This vulnerability arises from insufficient input validation and sanitization within the DHCP client's handling of various host name options received from remote DHCP servers. The affected options include HOST_NAME, DOMAIN_NAME, NIS_DOMAIN, and TFTP_SERVER_NAME, all of which are processed without proper shell escaping or validation, creating a pathway for remote attackers to execute arbitrary commands on systems running vulnerable versions of BusyBox.
The technical exploitation of this vulnerability occurs when a malicious DHCP server responds to a client's DHCP request with specially crafted option values containing shell metacharacters such as semicolons, pipes, or backticks. When the vulnerable udhcpc client processes these options, it directly incorporates the unvalidated input into shell commands without proper sanitization, enabling attackers to inject malicious commands that execute with the privileges of the DHCP client process. This represents a classic command injection vulnerability that falls under CWE-77, which specifically addresses command injection flaws where untrusted data is passed to an executable shell.
The operational impact of this vulnerability is severe and far-reaching across networked environments that rely on BusyBox-based systems for DHCP client functionality. Systems running vulnerable versions of udhcpc are at risk of complete compromise when they receive DHCP responses from malicious servers, particularly in environments where network infrastructure devices such as routers, switches, or embedded systems may be vulnerable. The vulnerability affects any system that uses the affected DHCP client to process network configuration options, including IoT devices, embedded systems, and network appliances that depend on BusyBox for their networking capabilities. Attackers can leverage this vulnerability to gain unauthorized access, execute arbitrary code, establish persistence, or perform reconnaissance activities within the compromised network segments.
This vulnerability aligns with several ATT&CK techniques including T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation. The attack surface is particularly concerning in enterprise environments where DHCP servers are not properly secured or monitored, as attackers can potentially deploy this vulnerability as part of broader network infiltration campaigns. Organizations should consider implementing network segmentation to isolate DHCP traffic, deploying DHCP snooping mechanisms, and ensuring all systems are updated to versions of BusyBox that properly sanitize DHCP option values. The vulnerability also highlights the importance of input validation in embedded systems and network infrastructure components, where security considerations are often secondary to functionality and performance requirements. Remediation requires updating to BusyBox version 1.20.0 or later, which implements proper input sanitization for DHCP options, or applying vendor-specific patches that address the command injection vulnerability through proper shell escaping mechanisms and input validation routines.