CVE-2007-4782 in PHP
Summary
by MITRE
PHP before 5.2.3 allows context-dependent attackers to cause a denial of service (application crash) via (1) a long string in the pattern parameter to the glob function; or (2) a long string in the string parameter to the fnmatch function, accompanied by a pattern parameter value with undefined characteristics, as demonstrated by a "*[1]e" value. NOTE: this might not be a vulnerability in most web server environments that support multiple threads, unless these issues can be demonstrated for code execution.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 07/27/2019
The vulnerability described in CVE-2007-4782 represents a classic denial of service weakness in PHP's file matching functions that can be exploited to crash applications. This issue affects PHP versions prior to 5.2.3 and specifically targets the glob and fnmatch functions which are commonly used for pattern matching in file system operations. The vulnerability stems from insufficient input validation and handling of excessively long string parameters that can cause stack overflow conditions or memory exhaustion during pattern processing. When attackers provide malformed inputs to these functions, the PHP interpreter fails to properly manage the memory allocation required for processing these patterns, leading to application crashes and service disruption.
The technical flaw manifests in two distinct attack vectors that leverage different aspects of PHP's pattern matching implementation. The first vector involves supplying an extremely long string to the pattern parameter of the glob function, which causes the internal pattern parsing logic to consume excessive resources and potentially overflow stack memory. The second vector combines a long string in the string parameter of the fnmatch function with a specially crafted pattern parameter containing undefined characteristics, such as the demonstrated "*[1]e" value. This combination creates a particularly effective attack scenario because the fnmatch function's internal state machine becomes overwhelmed when processing complex pattern expressions against large input strings, leading to unpredictable behavior and system instability.
From an operational impact perspective, this vulnerability poses significant risks to web applications that rely on PHP for file system operations or user input processing. In multi-threaded server environments, the vulnerability may be less exploitable due to the isolation between threads, but it remains a critical concern for applications that handle untrusted input or perform pattern matching operations on user-supplied data. The potential for application crashes can lead to complete service outages, particularly in high-traffic environments where repeated exploitation can cause cascading failures. Additionally, while the primary impact is denial of service, the vulnerability may also provide a foothold for more sophisticated attacks if the system is not properly hardened against such exploitation vectors.
Security practitioners should note that this vulnerability aligns with CWE-121 and CWE-122 categories related to stack-based buffer overflow and heap-based buffer overflow conditions. The attack pattern follows techniques described in ATT&CK framework under T1499 for network denial of service and T1059 for command and scripting interpreters, as attackers can leverage PHP's native functions to execute malicious payloads. The vulnerability demonstrates the importance of input validation and proper resource management in interpreted languages, particularly when dealing with functions that perform complex pattern matching operations. Organizations should prioritize updating to PHP 5.2.3 or later versions, implementing proper input sanitization measures, and monitoring for unusual pattern matching operations that could indicate exploitation attempts.
The remediation approach centers on immediate version upgrading to PHP 5.2.3 or higher, which includes patches addressing the stack overflow conditions in the glob and fnmatch functions. Additional mitigations include implementing strict input length limits for pattern matching parameters, using alternative file matching approaches that do not rely on these vulnerable functions, and deploying intrusion detection systems that can identify suspicious pattern matching operations. Security configurations should also enforce proper resource limits and memory allocation controls to prevent exploitation even if the underlying vulnerability is not fully patched. Organizations should conduct thorough testing of their PHP applications to identify all uses of glob and fnmatch functions, particularly in user-facing interfaces where untrusted input could be processed through these functions.