CVE-2006-1990 in PHP
Summary
by MITRE
Integer overflow in the wordwrap function in string.c in PHP 4.4.2 and 5.1.2 might allow context-dependent attackers to execute arbitrary code via certain long arguments that cause a small buffer to be allocated, which triggers a heap-based buffer overflow in a memcpy function call, a different vulnerability than CVE-2002-1396.
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Analysis
by VulDB Data Team • 03/12/2021
The vulnerability described in CVE-2006-1990 represents a critical integer overflow flaw within PHP's string handling mechanisms that can lead to remote code execution. This vulnerability specifically affects PHP versions 4.4.2 and 5.1.2, where the wordwrap function in string.c contains a flaw that manipulates integer values during buffer allocation calculations. The issue stems from the improper handling of large input arguments that cause integer overflow conditions, resulting in miscalculations of buffer sizes. When attackers provide carefully crafted long arguments to the wordwrap function, the integer overflow causes the system to allocate a buffer that is significantly smaller than required, creating a heap-based buffer overflow condition. This vulnerability operates through a classic heap corruption attack vector where the maliciously calculated buffer size leads to memory corruption during subsequent memcpy operations. The flaw is particularly dangerous because it leverages context-dependent attack conditions, meaning the vulnerability can be exploited when specific environmental factors align with the attacker's control over input parameters.
The technical implementation of this vulnerability demonstrates a sophisticated exploitation pathway that combines integer arithmetic manipulation with memory management flaws. The wordwrap function processes text wrapping operations by calculating how to break lines based on specified width parameters, but when these parameters exceed certain thresholds, integer overflow occurs in the size calculation logic. This overflow results in a situation where the allocated buffer size becomes insufficient to hold the data being copied, causing the memcpy function to write beyond the allocated heap memory boundaries. The vulnerability is categorized under CWE-190 as an integer overflow condition, which directly leads to memory corruption vulnerabilities. The heap-based buffer overflow creates opportunities for attackers to overwrite adjacent memory locations, potentially allowing them to manipulate program execution flow, inject malicious code, or cause arbitrary code execution. The specific nature of this vulnerability makes it particularly challenging to detect and prevent through standard input validation measures since the overflow occurs during internal buffer calculations rather than at the input parsing stage.
The operational impact of CVE-2006-1990 extends far beyond simple denial of service conditions, presenting significant risks to web application security and system integrity. Web applications that utilize PHP's wordwrap function with user-controllable input parameters become vulnerable to remote code execution attacks, potentially allowing attackers to gain complete control over affected systems. The vulnerability's exploitation requires context-dependent conditions, meaning attackers must carefully craft inputs that trigger the specific integer overflow scenario, but this does not diminish its severity since such conditions can often be achieved through automated means. Systems running vulnerable PHP versions are particularly at risk in environments where user input is processed through wordwrap functionality, including content management systems, web forums, and any application that performs text formatting operations. The attack vector typically involves sending specially crafted text data to web applications that process this data through PHP's string manipulation functions, potentially leading to complete system compromise. Organizations utilizing affected PHP versions face substantial risk exposure, as this vulnerability can be exploited without requiring special privileges or extensive knowledge of the target system's internal workings.
Mitigation strategies for CVE-2006-1990 must address both immediate remediation and long-term security posture improvements to protect against similar vulnerabilities. The primary and most effective mitigation involves upgrading to PHP versions that contain patches for this specific vulnerability, as newer versions have corrected the integer overflow conditions in the wordwrap function. Organizations should also implement comprehensive input validation and sanitization measures that restrict the length and content of parameters passed to string manipulation functions, particularly those that may trigger buffer allocation calculations. The implementation of address space layout randomization and stack canaries can provide additional protection layers against exploitation attempts, though these measures are considered defensive rather than primary fixes. Security monitoring and intrusion detection systems should be configured to detect unusual patterns of text processing operations that might indicate exploitation attempts. Additionally, the use of PHP-specific security modules and web application firewalls can provide additional protection by filtering malicious inputs before they reach vulnerable functions. Organizations should also conduct regular security assessments and penetration testing to identify similar vulnerabilities in their PHP applications, as the underlying architectural flaw in integer overflow handling suggests potential for similar issues in other functions. The vulnerability's classification under ATT&CK technique T1059.007 for command and scripting interpreter demonstrates the broader threat landscape where such memory corruption vulnerabilities can enable attackers to execute arbitrary commands on compromised systems, making comprehensive mitigation essential for protecting organizational assets.