CVE-2019-18888 in Symfony
Summary
by MITRE
An issue was discovered in Symfony 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. If an application passes unvalidated user input as the file for which MIME type validation should occur, then arbitrary arguments are passed to the underlying file command. This is related to symfony/http-foundation (and symfony/mime in 4.3.x).
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Analysis
by VulDB Data Team • 02/26/2024
This vulnerability exists within the Symfony framework's MIME type validation functionality, specifically affecting versions from 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. The issue stems from insufficient input validation when processing user-provided file paths for MIME type detection, creating a potential command injection vector through the underlying file command execution. The vulnerability is classified as a command injection flaw that allows attackers to manipulate the file command's arguments by injecting malicious input into the file parameter, which then gets passed directly to the system command without proper sanitization.
The technical flaw manifests when applications utilize Symfony's HttpFoundation or Mime components to validate file MIME types by executing the system file command. When user input is passed directly as the file argument without proper validation or sanitization, attackers can inject additional arguments or commands that get executed by the underlying system. This occurs because the framework relies on the system's file command to determine MIME types, and the user-supplied file path is not properly escaped or validated before being passed to this external command. The vulnerability specifically impacts the file command execution mechanism, where argument injection can lead to arbitrary command execution on the server.
The operational impact of this vulnerability is significant as it can enable remote code execution on affected systems, allowing attackers to execute arbitrary commands with the privileges of the web server process. This represents a critical security risk that can lead to full system compromise, data exfiltration, or further lateral movement within a network. The vulnerability affects web applications built on Symfony that process user-uploaded files or validate file types, particularly those that use the HttpFoundation or Mime components for MIME type detection. Attackers can exploit this by crafting malicious file paths that include shell metacharacters or command separators, which then get interpreted by the system file command.
Organizations should immediately upgrade to patched versions of Symfony, specifically versions 2.8.51, 3.4.35, 4.2.12, and 4.3.8, which contain the necessary fixes for this vulnerability. Additionally, implementing proper input validation and sanitization measures is crucial, including the use of allowlists for valid file extensions and proper escaping of user input before any system command execution. The vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.001 for command and scripting interpreter. Security teams should also implement network monitoring to detect suspicious command execution patterns and consider implementing web application firewalls to block potentially malicious input patterns. Organizations using older Symfony versions should prioritize immediate migration to supported releases to prevent exploitation of this critical command injection vulnerability.