CVE-2017-7271 in Yii Framework
Summary
by MITRE
Reflected Cross-site scripting (XSS) vulnerability in Yii Framework before 2.0.11, when development mode is used, allows remote attackers to inject arbitrary web script or HTML via crafted request data that is mishandled on the debug-mode exception screen.
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Analysis
by VulDB Data Team • 11/22/2022
The CVE-2017-7271 vulnerability represents a critical reflected cross-site scripting flaw within the Yii Framework that specifically manifests when the application operates in development mode. This vulnerability stems from the framework's improper handling of user input within the debug exception screen, creating a pathway for remote attackers to execute malicious scripts. The vulnerability is particularly concerning because it leverages the very debugging functionality that developers rely on during application development, making it both accessible and potentially devastating in its impact. The flaw exists in Yii Framework versions prior to 2.0.11, indicating that a significant portion of applications using older versions would remain exposed to this risk.
The technical implementation of this vulnerability occurs through the framework's debug mode exception handling mechanism, which is designed to provide detailed error information to developers for troubleshooting purposes. When development mode is enabled, the framework displays exception details directly to users, including raw request data that is not properly sanitized or escaped. Attackers can craft malicious requests containing script tags or other HTML content that gets reflected back to the victim's browser through the debug screen, thereby executing arbitrary code in the context of the victim's session. This behavior aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as weaknesses in input validation and output encoding, specifically addressing the failure to properly escape output data in web applications.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform session hijacking, deface web applications, steal sensitive user data, or redirect victims to malicious websites. The vulnerability's exploitation becomes particularly dangerous when considering that development mode is often enabled in staging environments or during application deployment processes, making these systems prime targets for attackers seeking to gain unauthorized access. Security researchers have noted that the vulnerability can be leveraged to bypass certain security controls, as the debug screen typically operates with elevated privileges and may contain sensitive information about the application's internal structure and configuration. This aligns with ATT&CK technique T1059.007, which describes the use of scripting languages to execute commands, and T1566, which covers the exploitation of vulnerabilities in web applications.
Mitigation strategies for CVE-2017-7271 primarily focus on immediate framework updates to version 2.0.11 or later, which includes proper input sanitization and output escaping mechanisms within the debug mode functionality. Organizations should also implement strict environment controls to ensure that development mode is never enabled in production environments, as this eliminates the attack surface entirely. Additional protective measures include implementing content security policies that restrict script execution, deploying web application firewalls to detect and block malicious payloads, and conducting regular security audits to identify any remaining instances of development mode activation. The vulnerability serves as a reminder of the critical importance of proper input validation and output encoding practices, particularly in debug and development contexts where security controls may be relaxed. Security teams should also establish robust deployment processes that automatically disable development features in production environments, thereby preventing the accidental exposure of vulnerable functionality.