CVE-2018-19792 in OpenLiteSpeed
Summary
by MITRE
The server in LiteSpeed OpenLiteSpeed before 1.5.0 RC6 allows local users to cause a denial of service (buffer overflow) or possibly have unspecified other impact by creating a symlink through which the openlitespeed program can be invoked with a long command name (involving ../ characters), which is mishandled in the LshttpdMain::getServerRootFromExecutablePath function.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability identified as CVE-2018-19792 represents a critical buffer overflow flaw within the LiteSpeed OpenLiteSpeed web server software prior to version 1.5.0 RC6. This vulnerability exists in the server component of the software and specifically affects local users who can manipulate the execution environment through symbolic link manipulation. The flaw occurs when the openlitespeed program is invoked through a carefully crafted symlink that contains a long command name incorporating ../ characters. The underlying technical issue stems from improper handling of path resolution within the LshttpdMain::getServerRootFromExecutablePath function, which fails to properly validate or sanitize the command line arguments before processing them. This function is responsible for determining the server root directory based on the executable path, but it does not adequately protect against excessively long input strings that can exceed the allocated buffer space.
The operational impact of this vulnerability extends beyond simple denial of service, as it potentially allows for arbitrary code execution or other unspecified security impacts. When a local attacker creates a symlink with a maliciously constructed path containing multiple ../ sequences, the vulnerable software processes this input without proper bounds checking, leading to a buffer overflow condition. This type of vulnerability can be exploited to overwrite adjacent memory locations, potentially allowing an attacker to execute arbitrary code with the privileges of the running OpenLiteSpeed process. The vulnerability is particularly concerning because it operates at the local user level, meaning that an attacker with minimal system access can leverage this flaw to compromise the web server's integrity. The buffer overflow occurs during the initialization phase of the server when the executable path is being analyzed to determine the server root directory, making it a critical point of failure in the software's startup sequence.
The technical implementation of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow issues. The flaw demonstrates characteristics of privilege escalation through path manipulation and command injection vectors that are commonly categorized under ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. The vulnerability's exploitation requires the attacker to have local file system access to create symbolic links and control the execution environment, but once successful, it can provide a foothold for more extensive attacks. The LshttpdMain::getServerRootFromExecutablePath function serves as the primary attack surface where the flawed path resolution logic fails to account for the potential length of command line arguments, particularly when dealing with complex symbolic link structures containing multiple directory traversal sequences.
Mitigation strategies for this vulnerability require immediate patching of affected OpenLiteSpeed installations to version 1.5.0 RC6 or later, which contains the necessary fixes for the buffer overflow condition. System administrators should also implement proper file system permissions and access controls to limit local user capabilities that could enable symlink creation attacks. The fix typically involves implementing proper bounds checking and input validation within the getServerRootFromExecutablePath function to prevent buffer overflows when processing executable paths. Additional defensive measures include monitoring for unusual symlink creation patterns, implementing file integrity monitoring systems, and ensuring that the web server runs with minimal necessary privileges. Organizations should also conduct regular security assessments to identify similar path traversal vulnerabilities in other software components and implement secure coding practices that emphasize input validation and proper buffer management. The vulnerability serves as a reminder of the importance of secure path resolution and the dangers of inadequate bounds checking in system-level applications that handle user-provided input.