CVE-2012-4257 in Yet Another Question
Summary
by MITRE
Yaqas (Yet Another Question & Answer System) 1.0 Alpha 1 allows remote attackers to obtain sensitive information via an invalid character in the PHPSESSID, which reveals the installation path in an error message.
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Analysis
by VulDB Data Team • 01/16/2018
The vulnerability identified as CVE-2012-4257 affects Yaqas version 1.0 Alpha 1, a question and answer system implemented in PHP. This flaw represents a sensitive data exposure issue that occurs when the application processes invalid session identifiers, specifically those containing malformed characters in the PHPSESSID parameter. The vulnerability stems from inadequate input validation and error handling mechanisms within the application's session management component, creating a pathway for remote attackers to extract critical system information.
The technical exploitation of this vulnerability involves sending a specially crafted PHPSESSID parameter containing invalid characters to the application server. When the system attempts to process this malformed session identifier, it generates an error message that inadvertently includes the absolute installation path of the application on the server filesystem. This occurs because the application's error handling routine does not properly sanitize or filter input before displaying error messages to users, creating a classic information disclosure vulnerability. The flaw operates at the application layer and can be classified under CWE-200, which specifically addresses improper error handling that leads to information exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as the revealed installation path provides attackers with crucial reconnaissance data that can be leveraged for subsequent attacks. The exposed filesystem path can reveal directory structures, potentially indicating the presence of other sensitive files or directories, and may aid in identifying the server operating system and PHP configuration. This information disclosure creates a foundation for more sophisticated attacks, including path traversal exploits, local file inclusion vulnerabilities, or targeted attacks against specific server components. The vulnerability aligns with ATT&CK technique T1212, which covers exploitation of software vulnerabilities that lead to information disclosure.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and error handling practices within the application. The most effective approach involves sanitizing all user input, particularly session identifiers, before processing them within the application. Additionally, error messages should be generic and not reveal system-specific information to unauthorized users. Organizations should also implement proper logging mechanisms to detect unusual patterns of session identifier manipulation and consider implementing custom error pages that prevent the exposure of internal system details. The vulnerability highlights the importance of following secure coding practices as outlined in OWASP Top 10 and ISO/IEC 27001 security standards, particularly in areas related to input validation and error handling.