CVE-2006-1490 in PHP
Summary
by MITRE
PHP before 5.1.3-RC1 might allow remote attackers to obtain portions of memory via crafted binary data sent to a script that processes user input in the html_entity_decode function and sends the encoded results back to the client, aka a "binary safety" issue. NOTE: this issue has been referred to as a "memory leak," but it is an information leak that discloses memory contents.
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Analysis
by VulDB Data Team • 06/14/2025
The vulnerability described in CVE-2006-1490 represents a critical information disclosure flaw in PHP versions prior to 5.1.3-RC1 that stems from improper handling of binary data within the html_entity_decode function. This issue falls under the category of memory safety vulnerabilities and specifically demonstrates how improper input validation can lead to unintended data exposure. The vulnerability is classified as a memory disclosure issue where attackers can potentially access portions of memory contents through carefully crafted binary data that gets processed by the affected function.
The technical flaw manifests when PHP scripts process user input through the html_entity_decode function, which is designed to convert HTML entities back to their corresponding characters. However, in vulnerable versions, the function fails to properly validate or sanitize binary data, allowing malicious inputs to trigger memory dumping behavior. When the function encounters crafted binary sequences, it may inadvertently expose memory contents that were previously stored in the application's memory space, including potentially sensitive data such as session information, database credentials, or other application-specific data that might be stored in adjacent memory locations.
This vulnerability operates at the intersection of input validation and memory management within PHP's core processing functions, creating an information leak that can be exploited by remote attackers without requiring special privileges or authentication. The impact extends beyond simple data exposure, as the leaked memory contents could contain sensitive information that could be leveraged for further attacks, including session hijacking, credential theft, or application exploitation. The vulnerability demonstrates a classic case of improper memory bounds checking and input sanitization that violates fundamental security principles.
The operational impact of this vulnerability is significant for any web applications running affected PHP versions, particularly those that process user input through html_entity_decode or similar functions. Attackers can craft malicious payloads that, when processed by vulnerable applications, result in partial memory disclosure to the client. This information leak can be particularly damaging in environments where applications handle sensitive data or where memory contains authentication tokens, encryption keys, or other confidential information. The vulnerability affects the confidentiality aspect of the CIA triad and can be classified under CWE-200 (Information Exposure) and CWE-125 (Out-of-bounds Read) categories.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to version 5.1.3-RC1 or later, which includes proper input validation and memory boundary checking within the html_entity_decode function. Organizations should also implement input sanitization measures at multiple layers, including web application firewalls, input validation routines, and proper error handling that prevents memory contents from being exposed to end users. Additionally, security monitoring should be enhanced to detect unusual patterns in application behavior that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1005 (Data from Local System) and T1041 (Exfiltration Over C2 Channel) when exploited, making it a significant concern for defensive security operations.