CVE-2011-1930 in klibc
Summary
by MITRE
In klibc 1.5.20 and 1.5.21, the DHCP options written by ipconfig to /tmp/net-$DEVICE.conf are not properly escaped. This may allow a remote attacker to send a specially crafted DHCP reply which could execute arbitrary code with the privileges of any process which sources DHCP options.
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Analysis
by VulDB Data Team • 09/12/2024
The vulnerability identified as CVE-2011-1930 resides within the klibc library version 1.5.20 and 1.5.21, specifically affecting the ipconfig utility's handling of DHCP options. This flaw represents a classic command injection vulnerability that arises from improper input sanitization during the processing of network configuration data. The issue occurs when ipconfig writes DHCP options to the temporary configuration file located at /tmp/net-$DEVICE.conf, where the data is not adequately escaped before being written to disk. This creates a dangerous scenario where remote attackers can manipulate DHCP responses to inject malicious content that gets executed when processes source the configuration file.
The technical implementation of this vulnerability stems from the failure to properly sanitize DHCP option data before it is written to a file that will later be sourced by system processes. When a DHCP server responds with specially crafted options containing unescaped characters, these values are directly written to the configuration file without proper encoding or validation. The vulnerability manifests when processes that use the ipconfig utility later source this file, typically through shell execution or configuration parsing mechanisms. This allows attackers to inject shell commands or other malicious content that executes with the privileges of the process performing the source operation, potentially leading to arbitrary code execution on the target system.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it creates a persistent threat vector that can be exploited across multiple system components. Any process that sources the DHCP configuration file from /tmp/net-$DEVICE.conf becomes a potential attack surface, including network management utilities, system initialization scripts, and various network configuration tools. The temporary nature of the file location at /tmp/ provides additional attack vectors since this directory is often world-writable and accessible to unprivileged users, making the exploitation more feasible. This vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and demonstrates how seemingly benign configuration file handling can create critical security weaknesses.
Mitigation strategies for CVE-2011-1930 must address both the immediate exploitation vectors and the underlying architectural issues. The most effective approach involves implementing proper input validation and escaping mechanisms within the ipconfig utility to ensure that DHCP options are sanitized before being written to configuration files. System administrators should also consider implementing stricter file permissions on temporary directories and monitoring for unauthorized modifications to DHCP configuration files. Additionally, network segmentation and DHCP server hardening measures can reduce the attack surface by limiting the ability of remote attackers to inject malicious DHCP responses. This vulnerability demonstrates the importance of input validation across all system components and aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter execution, highlighting how improper input handling can lead to arbitrary code execution through shell-based attacks.