CVE-2007-1883 in PHP
Summary
by MITRE
PHP 4.0.0 through 4.4.6 and 5.0.0 through 5.2.1 allows context-dependent attackers to read arbitrary memory locations via an interruption that triggers a user space error handler that changes a parameter to an arbitrary pointer, as demonstrated via the iptcembed function, which calls certain convert_to_* functions with its input parameters.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability identified as CVE-2007-1883 represents a critical memory corruption issue affecting PHP versions ranging from 4.0.0 through 4.4.6 and 5.0.0 through 5.2.1. This flaw resides in the core PHP interpreter's handling of user space error handlers and parameter processing within specific functions. The vulnerability manifests when an interruption occurs during execution, triggering a user space error handler that subsequently modifies a parameter to point to an arbitrary memory location. This type of vulnerability falls under the category of memory safety issues and is particularly dangerous because it can be exploited to read arbitrary memory locations, potentially exposing sensitive data or system information. The exploit specifically targets the iptcembed function, which internally invokes convert_to_* functions with input parameters that become manipulated during error handling.
The technical implementation of this vulnerability exploits the interaction between PHP's error handling mechanism and its type conversion functions. When the iptcembed function processes input parameters, it passes these values to convert_to_* functions that perform type conversions. During this process, if an error occurs and a user-defined error handler is invoked, the handler can modify the parameter reference to point to arbitrary memory addresses. This modification occurs because the error handler has access to the parameter variables and can manipulate their values before the function continues execution. The vulnerability stems from insufficient validation of parameter references during error handler execution, allowing attackers to redirect memory access through controlled parameter manipulation.
The operational impact of CVE-2007-1883 is significant, as it enables context-dependent attackers to potentially access sensitive memory contents that could include system information, user data, or application secrets. This type of vulnerability can be particularly dangerous in web applications where PHP processes user input, as it allows for information disclosure attacks that could lead to further exploitation. Attackers could leverage this vulnerability to read memory contents that might contain database credentials, session tokens, or other sensitive application data. The vulnerability's exploitation requires specific conditions involving error handling and parameter modification, making it somewhat more complex to exploit than simpler buffer overflow vulnerabilities, but still represents a serious security risk that could compromise entire applications or systems.
The vulnerability aligns with CWE-125, which describes "Out-of-bounds Read" conditions in software, and represents a classic example of how improper error handling can lead to memory safety issues. From an attack perspective, this vulnerability maps to techniques described in the ATT&CK framework under T1059 for command and scripting interpreter usage, and potentially T1068 for exploit for privilege escalation. The vulnerability demonstrates how improper parameter validation and error handler interaction can create dangerous conditions where attackers can manipulate program flow and memory access patterns. Organizations should prioritize patching affected PHP versions and implementing proper input validation to prevent exploitation. The recommended mitigation involves upgrading to patched PHP versions, implementing strict error handling procedures, and monitoring for suspicious memory access patterns in application logs. Additionally, defensive measures such as address space layout randomization and stack canaries can provide additional protection against exploitation attempts.