CVE-2011-1464 in PHP
Summary
by MITRE
Buffer overflow in the strval function in PHP before 5.3.6, when the precision configuration option has a large value, might allow context-dependent attackers to cause a denial of service (application crash) via a small numerical value in the argument.
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Analysis
by VulDB Data Team • 10/20/2021
The vulnerability identified as CVE-2011-1464 represents a critical buffer overflow flaw within PHP's strval function that existed in versions prior to 5.3.6. This security issue stems from improper handling of numerical values when the precision configuration option is set to extremely large values, creating a scenario where attackers can exploit the application's memory management to cause unexpected behavior. The flaw specifically manifests when PHP processes numerical arguments through the strval function, which converts numeric values to string representations, but fails to properly validate the memory allocation required for such conversions.
The technical implementation of this vulnerability exploits the interaction between PHP's internal precision handling and memory allocation mechanisms. When the precision configuration option is configured with excessively large values, the strval function attempts to allocate memory buffers that exceed reasonable limits, creating a situation where a small numerical input can trigger an enormous memory allocation request. This improper memory management creates a buffer overflow condition that can lead to application instability and potential system crashes. The vulnerability is context-dependent because it requires specific configuration settings to be present, making it less likely to occur in default installations but still exploitable in environments where administrators configure high precision values for numerical processing.
The operational impact of CVE-2011-1464 extends beyond simple denial of service, as it can potentially allow attackers to cause application crashes that may be exploited for more sophisticated attacks. When an application crashes due to this buffer overflow, it creates opportunities for service disruption that can affect availability and potentially provide attackers with information about the system's internal state. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of improper input validation leading to memory corruption. Attackers can leverage this vulnerability by crafting specific numerical inputs that, when processed through the strval function with high precision settings, trigger the buffer overflow condition and cause the targeted application to crash.
Mitigation strategies for CVE-2011-1464 primarily focus on updating PHP installations to versions 5.3.6 or later, where the buffer overflow has been addressed through improved memory allocation and input validation mechanisms. System administrators should also review and restrict the precision configuration options in PHP installations, particularly in environments where untrusted input is processed, to prevent attackers from exploiting the vulnerability through configuration manipulation. The implementation of proper input validation and sanitization practices can further reduce the attack surface by ensuring that numerical values passed to strval functions are within reasonable bounds. Additionally, monitoring and logging mechanisms should be implemented to detect unusual memory allocation patterns that may indicate exploitation attempts, providing early warning capabilities for potential attacks targeting this vulnerability. Organizations should also consider implementing application-level firewalls and intrusion detection systems that can identify and block malicious numerical inputs designed to trigger buffer overflow conditions in PHP applications.
This vulnerability demonstrates the importance of proper memory management in scripting languages and highlights how seemingly benign configuration options can create security risks when combined with specific processing functions. The issue reflects broader concerns in software security related to integer overflows and memory corruption vulnerabilities that continue to pose significant threats to web application security. The remediation approach for CVE-2011-1464 emphasizes the fundamental principle that all input processing functions should include proper bounds checking and memory allocation validation to prevent buffer overflow conditions that can lead to system instability and potential exploitation.