CVE-2021-43691 in tripexpress
Summary
by MITRE • 11/29/2021
An unspecified version of tripexpress is affected by a path manipulation vulnerability in file system/helpers/dompdf/load_font.php. The variable src is coming from $_SERVER["argv"] then there is a path manipulation vulnerability.
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Analysis
by VulDB Data Team • 12/02/2021
The vulnerability identified as CVE-2021-43691 represents a critical path manipulation flaw within the tripexpress application ecosystem, specifically within the file system/helpers/dompdf/load_font.php component. This issue arises from improper handling of user-supplied input that originates from the command line arguments passed through the $_SERVER["argv"] superglobal variable. The vulnerability classification aligns with CWE-73, which describes improper neutralization of special elements used in resource identifiers, and specifically relates to path traversal scenarios where external input directly influences file system operations.
The technical exploitation of this vulnerability occurs when the application processes command line arguments without adequate sanitization or validation of the source parameter. When the src variable is populated from $_SERVER["argv"], it becomes susceptible to manipulation by attackers who can inject malicious path sequences such as directory traversal characters or absolute path references. The dompdf library component, which handles font loading operations, becomes the vector through which this manipulation can be leveraged to access unauthorized file system resources, potentially leading to arbitrary file read operations or even code execution depending on the application's file system permissions.
From an operational impact perspective, this vulnerability presents significant security risks to organizations utilizing tripexpress applications, particularly those operating in environments where command line interfaces are exposed to untrusted inputs or where the application executes with elevated privileges. The vulnerability could enable attackers to bypass normal access controls and potentially read sensitive configuration files, database credentials, or other critical system information stored in accessible file locations. The ATT&CK framework categorizes this as a Path Traversal technique under the T1083 discovery tactic, where adversaries seek to enumerate and access files and directories they normally would not have access to.
Mitigation strategies for this vulnerability should focus on implementing strict input validation and sanitization of all command line arguments before they are processed by the dompdf library or any other file system operations. Organizations should employ proper parameter validation techniques that reject or escape any input containing path traversal sequences such as .. or /../. The implementation of a whitelist approach for acceptable font file paths, combined with privilege reduction measures for the application processes, can significantly limit the potential impact of this vulnerability. Additionally, regular security audits and code reviews should specifically target file system operations that utilize user-supplied input to prevent similar issues from emerging in other components of the application stack.