CVE-2017-16654 in Symfony
Summary
by MITRE
An issue was discovered in Symfony before 2.7.38, 2.8.31, 3.2.14, 3.3.13, 3.4-BETA5, and 4.0-BETA5. The Intl component includes various bundle readers that are used to read resource bundles from the local filesystem. The read() methods of these classes use a path and a locale to determine the language bundle to retrieve. The locale argument value is commonly retrieved from untrusted user input (like a URL parameter). An attacker can use this argument to navigate to arbitrary directories via the dot-dot-slash attack, aka Directory Traversal.
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Analysis
by VulDB Data Team • 05/01/2023
The vulnerability identified as CVE-2017-16654 affects the Symfony PHP framework and represents a critical directory traversal flaw within its Intl component. This vulnerability exists in versions prior to 2.7.38, 2.8.31, 3.2.14, 3.3.13, 3.4-BETA5, and 4.0-BETA5, exposing applications that utilize Symfony's internationalization features to potential exploitation. The core issue lies in how the framework handles locale parameter input within its bundle reader implementations, creating a pathway for attackers to access arbitrary files on the server's filesystem through manipulation of path traversal sequences.
The technical flaw manifests in the read() methods of various bundle reader classes within Symfony's Intl component that process user-supplied locale values to determine which language bundle to retrieve. These methods accept both a path parameter and a locale parameter, where the locale parameter is typically derived from untrusted user input such as URL parameters or HTTP headers. When attackers supply malicious locale values containing sequences like "../", they can navigate beyond the intended directory boundaries and access files outside the intended resource bundle locations. This vulnerability is classified as a directory traversal attack, specifically leveraging dot-dot-slash sequences to move up the directory hierarchy and access restricted filesystem locations.
The operational impact of this vulnerability is severe and multifaceted, as it allows attackers to potentially read sensitive files from the server's filesystem including configuration files, database credentials, application source code, and other confidential information. Attackers could exploit this vulnerability to gain unauthorized access to critical system resources, potentially leading to full system compromise. The vulnerability is particularly dangerous because it can be exploited through common web application attack vectors such as URL parameters, making it easily accessible to threat actors without requiring special privileges or complex exploitation techniques. This flaw directly maps to CWE-22 - Improper Limitation of a Pathname to a Restricted Directory and aligns with ATT&CK technique T1083 - File and Directory Discovery, as it enables attackers to enumerate and access arbitrary files on the target system.
Mitigation strategies for CVE-2017-16654 involve immediate upgrading to patched versions of Symfony framework components, specifically ensuring that applications are running on versions 2.7.38, 2.8.31, 3.2.14, 3.3.13, 3.4-BETA5, or 4.0-BETA5 and later. Organizations should also implement input validation and sanitization measures to filter and validate all user-supplied locale parameters before they are processed by the Intl component. Additionally, proper filesystem permissions should be enforced to limit access to sensitive files, and application firewalls or web application firewalls should be configured to detect and block suspicious path traversal attempts. The vulnerability demonstrates the importance of secure coding practices and input validation in web applications, particularly when handling user-supplied data that may be used in filesystem operations, aligning with security best practices outlined in OWASP Top Ten and NIST cybersecurity guidelines.