CVE-2007-5898 in PHP
Summary
by MITRE
The (1) htmlentities and (2) htmlspecialchars functions in PHP before 5.2.5 accept partial multibyte sequences, which has unknown impact and attack vectors, a different issue than CVE-2006-5465.
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Analysis
by VulDB Data Team • 11/04/2020
The vulnerability described in CVE-2007-5898 affects PHP versions prior to 5.2.5 and specifically targets the htmlentities and htmlspecialchars functions. This issue represents a critical security flaw in PHP's handling of multibyte character sequences, particularly when processing input that contains incomplete or partial multibyte characters. The vulnerability stems from the functions' inability to properly validate and process multibyte character encodings, creating potential attack vectors that could be exploited by malicious actors.
The technical flaw manifests when these PHP functions encounter partial multibyte sequences in input data. In normal operation, these functions should properly validate character boundaries and handle multibyte encodings according to established standards. However, the vulnerability allows attackers to craft input that contains incomplete multibyte characters, which the functions process without proper validation. This behavior creates a situation where the functions may interpret partial sequences as complete characters, leading to unpredictable behavior in the application's output processing and potentially enabling code injection or other malicious activities.
From an operational impact perspective, this vulnerability presents significant risks to web applications that rely on PHP's htmlentities and htmlspecialchars functions for input sanitization and output encoding. Applications using these functions to prevent cross-site scripting attacks or to sanitize user input may be vulnerable to bypass attacks where malicious input containing partial multibyte sequences can evade proper sanitization. The unknown impact and attack vectors mentioned in the CVE description indicate that the exact nature of exploitation methods remains unclear, but the potential for bypassing security controls is substantial. This vulnerability falls under the CWE-180 category of "Incorrect Behavior Order" and specifically relates to CWE-707, which deals with "Improper Neutralization of Special Elements in Output Used by a Downstream Component."
The attack surface for this vulnerability extends beyond simple XSS scenarios to potentially include code execution or data manipulation attacks. When applications process user input through these functions, attackers can exploit the partial multibyte sequence handling to craft inputs that may cause the functions to behave unexpectedly, potentially leading to injection attacks or other security bypasses. The vulnerability's relationship to CVE-2006-5465 indicates that while both issues involve multibyte character handling, they represent distinct problems in PHP's encoding validation mechanisms. This particular vulnerability demonstrates the complexity of handling multibyte character encodings in web applications and the critical importance of proper input validation and sanitization.
Organizations should implement immediate mitigation strategies including upgrading to PHP 5.2.5 or later versions where this vulnerability has been addressed. Additionally, administrators should review existing codebases to identify applications that rely on these functions and ensure proper input validation is implemented at multiple layers of the application stack. The remediation process should include comprehensive testing to verify that all input handling functions properly validate multibyte character sequences and that security controls remain effective against potential exploitation attempts. Security teams should also consider implementing runtime monitoring to detect anomalous behavior patterns that might indicate exploitation attempts targeting this vulnerability.