CVE-2012-0781 in PHP
Summary
by MITRE
The tidy_diagnose function in PHP 5.3.8 might allow remote attackers to cause a denial of service (NULL pointer dereference and application crash) via crafted input to an application that attempts to perform Tidy::diagnose operations on invalid objects, a different vulnerability than CVE-2011-4153.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2012-0781 represents a critical denial of service flaw within PHP's Tidy extension, specifically affecting PHP version 5.3.8 and potentially other versions within the 5.3.x series. This issue stems from improper handling of invalid objects during Tidy::diagnose operations, creating a scenario where remote attackers can exploit the function to crash applications through crafted input. The vulnerability manifests as a NULL pointer dereference that ultimately leads to application instability and complete system unavailability, making it particularly dangerous in production environments where service continuity is paramount.
The technical root cause of this vulnerability lies in the tidy_diagnose function's inadequate validation of input parameters before processing. When an application attempts to perform diagnostic operations on malformed or invalid objects, the Tidy extension fails to properly check for NULL references within its internal processing logic. This flaw operates at the intersection of memory management and input validation, where the function does not adequately sanitize or verify the object state before attempting to access its properties. According to CWE-476, this vulnerability maps directly to a NULL pointer dereference condition, which is classified as a fundamental memory safety issue that can lead to application crashes and system instability. The vulnerability's impact is amplified by its ability to be triggered remotely, making it accessible to attackers without requiring local system access or elevated privileges.
The operational implications of CVE-2012-0781 extend beyond simple service disruption, as it can be exploited to create persistent denial of service conditions that may require manual intervention to resolve. Applications utilizing the Tidy extension for HTML validation or cleanup operations become particularly vulnerable when they process untrusted input from users or external sources. Attackers can craft malicious payloads that, when processed through the Tidy::diagnose function, trigger the NULL pointer dereference and cause the application to crash. This vulnerability particularly affects web applications that use PHP's Tidy extension for content validation, HTML cleaning, or document processing tasks, creating a significant risk for content management systems, web applications, and any platform that relies on HTML processing capabilities. The vulnerability's similarity to CVE-2011-4153 indicates a pattern of issues within the Tidy extension that requires comprehensive review of the extension's input handling mechanisms.
Mitigation strategies for CVE-2012-0781 primarily focus on immediate version upgrades and input validation enhancements. Organizations should prioritize upgrading to PHP versions that contain patches for this vulnerability, specifically PHP 5.3.9 or later, which address the NULL pointer dereference issue through improved input validation and memory handling. Additionally, implementing comprehensive input sanitization measures can help reduce the attack surface by ensuring that all data processed through the Tidy extension is properly validated before being passed to diagnostic functions. Security teams should also consider implementing application-level monitoring to detect unusual patterns of Tidy::diagnose function usage that might indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1499.004 for network denial of service emphasizes the need for robust network-level protections and monitoring to detect and prevent exploitation attempts. Furthermore, organizations should conduct thorough code reviews to identify all instances where the Tidy extension is used and ensure that proper error handling and input validation are implemented to prevent similar issues from occurring in other parts of the application stack.