CVE-2017-17562 in Integrated Lights Out Manager
Summary
by MITRE
Embedthis GoAhead before 3.6.5 allows remote code execution if CGI is enabled and a CGI program is dynamically linked. This is a result of initializing the environment of forked CGI scripts using untrusted HTTP request parameters in the cgiHandler function in cgi.c. When combined with the glibc dynamic linker, this behaviour can be abused for remote code execution using special parameter names such as LD_PRELOAD. An attacker can POST their shared object payload in the body of the request, and reference it using /proc/self/fd/0.
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Analysis
by VulDB Data Team • 02/05/2025
This vulnerability exists in Embedthis GoAhead web server versions prior to 3.6.5 and represents a critical remote code execution flaw that leverages improper environment variable handling during CGI script execution. The vulnerability stems from the cgiHandler function in cgi.c which initializes the environment of forked CGI scripts using untrusted HTTP request parameters without adequate sanitization or validation. When CGI functionality is enabled and a CGI program is dynamically linked, this flaw creates a pathway for attackers to inject malicious environment variables that can be exploited through the glibc dynamic linker mechanism.
The technical exploitation occurs through the manipulation of specific environment variable names that are processed by the dynamic linker, most notably LD_PRELOAD which allows attackers to preload malicious shared libraries before the execution of legitimate programs. Attackers can craft HTTP POST requests that include specially formatted parameters which get passed to the CGI environment, enabling them to specify shared library paths that will be loaded during the execution of the CGI script. The vulnerability is particularly dangerous because it allows attackers to upload their malicious payload directly in the request body and reference it using the special /proc/self/fd/0 path, which points to the standard input stream of the current process, effectively allowing remote code execution without requiring persistent storage on the target system.
The operational impact of this vulnerability is severe as it enables full remote code execution on systems running vulnerable versions of GoAhead web server, potentially allowing attackers to gain complete control over the affected system. This represents a privilege escalation vulnerability that can be exploited from any remote location without requiring authentication, making it particularly dangerous for publicly accessible web servers. The vulnerability affects systems where CGI is enabled and CGI programs are dynamically linked, which is common in many web server configurations, and the attack can be performed through standard HTTP traffic that may not be easily detected by traditional network monitoring tools.
Mitigation strategies should focus on immediate patching of the GoAhead web server to version 3.6.5 or later, which contains the necessary fixes for the environment variable handling in the CGI module. Organizations should also consider disabling CGI functionality if it is not required for their specific use cases, as this removes the attack surface entirely. Additionally, network administrators should implement strict input validation and sanitization for HTTP request parameters, and consider using web application firewalls to detect and block suspicious parameter patterns. The vulnerability aligns with CWE-74 which describes improper neutralization of special elements in output used by a downstream component, and maps to ATT&CK technique T1059.007 for command and scripting interpreter, specifically focusing on the use of CGI scripts for code execution. Organizations should also review their system configurations to ensure that CGI programs are not unnecessarily dynamically linked, as this reduces the attack surface for exploitation through the glibc dynamic linker mechanism.