CVE-2017-8411 in DCS-1130
Summary
by MITRE
An issue was discovered on D-Link DCS-1130 devices. The device provides a user with the capability of setting a SMB folder for the video clippings recorded by the device. It seems that the POST parameters passed in this request (to test if email credentials and hostname sent to the device work properly) result in being passed as commands to a "system" API in the function and thus result in command injection on the device. If the firmware version is dissected using binwalk tool, we obtain a cramfs-root archive which contains the filesystem set up on the device that contains all the binaries. The library "libmailutils.so" is the one that has the vulnerable function "sub_1FC4" that receives the values sent by the POST request. If we open this binary in IDA-pro we will notice that this follows an ARM little endian format. The function sub_1FC4 in IDA pro is identified to be receiving the values sent in the POST request and the value set in POST parameter "receiver1" is extracted in function "sub_15AC" which is then passed to the vulnerable system API call. The vulnerable library function is accessed in "cgibox" binary at address 0x00023BCC which calls the "Send_mail" function in "libmailutils.so" binary as shown below which results in the vulnerable POST parameter being passed to the library which results in the command injection issue.
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Analysis
by VulDB Data Team • 10/15/2023
The vulnerability identified in D-Link DCS-1130 devices through CVE-2017-8411 represents a critical command injection flaw that stems from improper input validation within the device's email configuration functionality. This issue specifically affects the device's ability to test email credentials and hostname settings through a POST request mechanism designed to verify connectivity before storing video clippings in an SMB folder. The vulnerability manifests when the system processes parameters sent via HTTP POST requests intended for email credential validation, ultimately passing these unvalidated inputs directly to the system API without proper sanitization or command encoding. This design flaw creates a pathway for malicious actors to execute arbitrary commands on the embedded device with the privileges of the web server process, potentially leading to complete system compromise.
The technical implementation of this vulnerability involves a specific function within the libmailutils.so library named sub_1FC4, which serves as the primary entry point for processing email-related parameters. When analyzing the firmware using tools like binwalk, the device's cramfs-root archive reveals the complete filesystem structure including all binaries and libraries. The vulnerable function sub_1FC4 receives values from POST parameters, particularly the "receiver1" parameter which is extracted in function sub_15AC and subsequently passed to the system API call. This architectural design fails to implement proper input validation or sanitization mechanisms, allowing attackers to inject malicious commands that get executed through the system call interface. The vulnerability exists in the cgibox binary at address 0x00023BCC where it calls the Send_mail function within libmailutils.so, creating a direct code execution path from user-controllable input to system command execution.
The operational impact of this command injection vulnerability extends beyond simple privilege escalation to encompass full system compromise and potential data exfiltration. Attackers can leverage this vulnerability to execute arbitrary system commands, potentially gaining access to sensitive device configuration information, network credentials, or even establishing persistent backdoors. The ARM little endian architecture of the device does not provide inherent protection against this type of injection, as the vulnerability lies in the software implementation rather than the processor architecture. The vulnerability affects the device's ability to securely handle user inputs during email configuration testing, creating a persistent threat vector that remains active as long as the device operates with the vulnerable firmware version. This type of vulnerability falls under CWE-77 and CWE-78 categories, representing command injection flaws that allow arbitrary command execution through improper input validation.
Mitigation strategies for this vulnerability should include immediate firmware updates from D-Link to address the specific command injection flaw in the libmailutils.so library. Network segmentation and access control measures should be implemented to limit direct access to the device's web interface, reducing the attack surface for potential exploitation. Regular firmware updates and security audits should be conducted to identify and remediate similar vulnerabilities in embedded systems. The ATT&CK framework categorizes this vulnerability under T1059.001 (Command and Scripting Interpreter: PowerShell) and T1059.007 (Command and Scripting Interpreter: Python) as it enables arbitrary command execution through web-based interfaces. Organizations should implement network monitoring to detect unusual command execution patterns and establish secure coding practices that emphasize input validation and parameter sanitization for all user-controllable inputs. Additionally, the vulnerability demonstrates the importance of secure configuration management for embedded devices, particularly those handling network communications and file system operations that could expose system-level functionality to remote attackers.