CVE-2007-4784 in PHP
Summary
by MITRE
The setlocale function in PHP before 5.2.4 allows context-dependent attackers to cause a denial of service (application crash) via a long string in the locale parameter. NOTE: this might not be a vulnerability in most web server environments that support multiple threads, unless this issue can be demonstrated for code execution.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability described in CVE-2007-4784 affects the setlocale function in PHP versions prior to 5.2.4, representing a denial of service weakness that can be exploited through carefully crafted input. This flaw resides in the locale parameter processing mechanism where the function fails to properly handle excessively long string inputs, leading to application instability and potential system crashes. The vulnerability operates within the broader context of PHP's internationalization and localization capabilities, which are essential for web applications serving global audiences but become problematic when input validation mechanisms are insufficient. The issue demonstrates a classic buffer handling problem where the system does not adequately validate the length of user-supplied locale identifiers, creating an opportunity for attackers to disrupt service availability.
The technical implementation of this vulnerability stems from inadequate bounds checking within the setlocale function's string processing routines. When PHP encounters a malformed locale parameter containing an excessive string length, the internal memory management routines fail to properly handle the allocation and processing of this input, resulting in stack corruption or memory exhaustion conditions that cause the application to terminate unexpectedly. This behavior aligns with CWE-122, which describes buffer overflow conditions in heap-based memory allocation, and reflects improper input validation practices that have been consistently identified as critical security weaknesses in web application frameworks. The vulnerability's exploitation requires context-dependent conditions where attackers can influence the locale parameter through user input, typically via GET or POST parameters in web applications that utilize PHP's localization features.
The operational impact of CVE-2007-4784 extends beyond simple service disruption to potentially compromise the stability of entire web server environments, particularly when multiple concurrent requests are processed. In multi-threaded web server configurations, the vulnerability may manifest differently than in single-threaded environments, though it remains capable of causing application crashes that can be leveraged for sustained denial of service attacks. The potential for code execution, while noted as uncertain in the original advisory, cannot be entirely dismissed given that application crashes often represent precursors to more serious exploitation vectors. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under ATT&CK technique T1499.004, which covers network denial of service attacks, though the specific vector involves application-level rather than network-level disruption.
Mitigation strategies for this vulnerability primarily focus on immediate patching of affected PHP installations to version 5.2.4 or later, where the input validation has been strengthened to prevent excessive string processing. System administrators should implement comprehensive input validation at multiple layers, including web application firewalls and application-level filters that sanitize locale parameters before they reach the PHP engine. Additionally, deploying monitoring solutions that can detect anomalous request patterns and implementing rate limiting mechanisms can help prevent exploitation attempts. Organizations should also conduct thorough security assessments of their web applications to identify all potential entry points where user-supplied locale data might be processed, ensuring that proper bounds checking is implemented throughout the application stack. The vulnerability serves as a reminder of the critical importance of input validation in preventing both denial of service and potential privilege escalation scenarios in web-based applications.