CVE-2004-1019 in PHP
Summary
by MITRE
The deserialization code in PHP before 4.3.10 and PHP 5.x up to 5.0.2 allows remote attackers to cause a denial of service and execute arbitrary code via untrusted data to the unserialize function that may trigger "information disclosure, double-free and negative reference index array underflow" results.
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Analysis
by VulDB Data Team • 06/30/2019
The vulnerability identified as CVE-2004-1019 represents a critical security flaw in PHP's serialization and deserialization mechanisms that affected versions prior to PHP 4.3.10 and PHP 5.0.2. This vulnerability resides in the unserialize function's handling of untrusted data, creating a dangerous attack surface that allows remote adversaries to exploit multiple types of memory corruption issues. The flaw specifically manifests when PHP processes serialized data from untrusted sources, enabling attackers to craft malicious payloads that can trigger severe system instability and arbitrary code execution. The vulnerability operates at the core of PHP's object serialization framework, where the deserialization process fails to properly validate or sanitize input data before processing it.
The technical implementation of this vulnerability stems from insufficient bounds checking and validation within PHP's internal deserialization routines. When the unserialize function encounters specially crafted serialized data, it can trigger several distinct memory corruption scenarios including information disclosure, double-free errors, and negative reference index array underflows. These memory corruption conditions occur because PHP's deserialization code does not adequately validate the structure and contents of serialized data before attempting to reconstruct objects. The double-free condition arises when the same memory block gets freed twice during object reconstruction, potentially allowing attackers to manipulate heap memory. Information disclosure vulnerabilities occur when the deserialization process leaks sensitive memory contents, while negative reference index array underflows happen when array indexing operations access memory locations before the beginning of allocated arrays. This vulnerability is classified under CWE-122 as "Heap-based Buffer Overflow" and CWE-125 as "Out-of-bounds Read" within the CWE dictionary, representing fundamental memory safety issues in the language's core functionality.
The operational impact of CVE-2004-1019 extends beyond simple denial of service to encompass full system compromise capabilities, making it particularly dangerous for web applications running PHP. Attackers can leverage this vulnerability to execute arbitrary code on vulnerable systems, potentially gaining complete control over web servers hosting PHP applications. The vulnerability affects a wide range of web applications including content management systems, e-commerce platforms, and custom web applications that utilize PHP's serialization features for data persistence or communication. Remote exploitation is possible because the vulnerability can be triggered through user input that gets serialized and later deserialized, such as session data, cookie values, or parameters passed to PHP functions. This makes it particularly dangerous for applications that store user-provided data in serialized form, as attackers can craft malicious serialized data that, when processed by the vulnerable unserialize function, results in code execution. The ATT&CK framework categorizes this vulnerability under T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1203 for "Exploitation for Client Execution" due to its ability to execute arbitrary code through deserialization attacks.
Mitigation strategies for CVE-2004-1019 primarily focus on immediate version upgrades to patched PHP releases, specifically PHP 4.3.10 and PHP 5.0.2 or later versions. Organizations should implement comprehensive patch management procedures to ensure all PHP installations are updated promptly. Additionally, input validation and sanitization practices should be strengthened to prevent untrusted data from reaching the unserialize function, particularly in session management and data persistence components. Application developers should avoid using unserialize with user-provided data whenever possible, implementing alternative data exchange mechanisms such as JSON or XML parsing with proper validation. Security monitoring should be enhanced to detect unusual patterns in serialized data processing, and network segmentation can help limit the potential impact of successful exploitation attempts. The vulnerability highlights the critical importance of secure coding practices in language implementations, particularly around memory management and input validation, and serves as a reminder of the dangers inherent in improper handling of serialized data in web applications.