CVE-2007-0907 in PHP
Summary
by MITRE
Buffer underflow in PHP before 5.2.1 allows attackers to cause a denial of service via unspecified vectors involving the sapi_header_op function.
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Analysis
by VulDB Data Team • 07/13/2021
The vulnerability identified as CVE-2007-0907 represents a critical buffer underflow condition within the PHP scripting language implementation prior to version 5.2.1. This flaw specifically manifests within the sapi_header_op function which serves as a crucial component for handling HTTP header operations in the Server Application Programming Interface. The buffer underflow occurs when the application processes certain HTTP header data, creating a scenario where memory operations exceed allocated boundaries. Such conditions typically arise when the application fails to properly validate the length or content of header data before processing, leading to unpredictable memory corruption patterns that can be exploited by malicious actors.
The technical nature of this vulnerability places it firmly within the category of memory safety issues, specifically classified under CWE-121 as buffer underflow conditions. The flaw enables attackers to manipulate the memory layout of the PHP application through crafted HTTP headers, potentially leading to arbitrary code execution or complete service disruption. The unspecified vectors mentioned in the description suggest that multiple attack paths exist through different header manipulation techniques, making the vulnerability particularly dangerous as defenders cannot easily predict all possible exploitation methods. The sapi_header_op function acts as a gateway for HTTP header processing, making it a prime target for attackers seeking to compromise web applications built on PHP platforms.
From an operational perspective, this vulnerability creates significant risk for web applications relying on PHP versions below 5.2.1, as it allows for denial of service attacks that can completely disable service availability. Attackers can craft malicious HTTP requests containing specially formatted headers that trigger the buffer underflow condition, causing the PHP process to crash or behave unpredictably. The impact extends beyond simple service disruption, as the memory corruption can potentially lead to privilege escalation or arbitrary code execution depending on the execution environment. Organizations running vulnerable PHP installations face substantial risk of service interruption and potential data exposure, particularly in environments where PHP handles sensitive user information or performs critical business functions.
The mitigation strategy for this vulnerability requires immediate patching of PHP installations to version 5.2.1 or later, which contains the necessary code fixes to prevent the buffer underflow condition in sapi_header_op. System administrators should also implement proper input validation measures at network boundaries and consider deploying intrusion detection systems that can identify and block suspicious header patterns. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all systems running vulnerable PHP versions and ensure proper patch management procedures are in place. The ATT&CK framework categorizes this vulnerability under T1499 as denial of service attacks, with potential progression to T1059 for command execution if exploitation leads to code execution capabilities. Regular security monitoring and application firewalls can provide additional layers of defense while the core patching effort is underway.