CVE-2007-1286 in PHP
Summary
by MITRE
Integer overflow in PHP 4.4.4 and earlier allows remote context-dependent attackers to execute arbitrary code via a long string to the unserialize function, which triggers the overflow in the ZVAL reference counter.
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Analysis
by VulDB Data Team • 12/27/2024
The vulnerability identified as CVE-2007-1286 represents a critical integer overflow flaw within PHP's unserialize function that existed in versions 4.4.4 and earlier. This vulnerability stems from inadequate input validation and handling of serialized data structures, specifically targeting the internal ZVAL reference counter mechanism that PHP employs to manage variable references. The flaw occurs when a maliciously crafted serialized string containing an excessively long value is processed through the unserialize function, creating conditions where integer arithmetic operations exceed the maximum representable value for the target platform's integer type.
The technical exploitation of this vulnerability relies on the manipulation of PHP's internal reference counting system, where each ZVAL structure maintains a reference counter to track how many variables reference the same data. When the unserialize function processes a crafted payload, it can cause this reference counter to overflow from its maximum positive value back to zero or negative values, leading to unpredictable behavior in memory management and potentially allowing attackers to manipulate memory layout. This integer overflow creates opportunities for memory corruption that can be leveraged to execute arbitrary code, as the overflowed counter may cause the system to allocate memory incorrectly or overwrite critical data structures.
From an operational perspective, this vulnerability presents a significant risk to web applications that utilize PHP's unserialize function to process user-supplied data or serialized objects from external sources. Attackers can craft malicious serialized strings that, when unserialized, trigger the integer overflow condition and potentially execute arbitrary code with the privileges of the web server process. The context-dependent nature of this vulnerability means that successful exploitation requires specific conditions, including the ability to inject serialized data into the application's input processing pipeline, but once achieved, the impact can be severe. The vulnerability aligns with CWE-190, which describes integer overflow conditions, and maps to ATT&CK technique T1190, representing the exploitation of vulnerabilities in application software.
Mitigation strategies for this vulnerability primarily involve immediate upgrades to PHP versions 5.0.0 or later, where the unserialize function was significantly improved and the integer overflow issue was addressed. Organizations should also implement strict input validation and sanitization for all serialized data, particularly when processing user-supplied content. Additional protective measures include restricting the use of unserialize functions in applications where possible, implementing proper access controls to limit data injection points, and conducting regular security assessments to identify potential exploitation vectors. The vulnerability serves as a reminder of the critical importance of proper integer handling in security-sensitive code and demonstrates how seemingly minor implementation flaws can result in severe remote code execution capabilities.