CVE-2018-7584 in macOS
Summary
by MITRE
In PHP through 5.6.33, 7.0.x before 7.0.28, 7.1.x through 7.1.14, and 7.2.x through 7.2.2, there is a stack-based buffer under-read while parsing an HTTP response in the php_stream_url_wrap_http_ex function in ext/standard/http_fopen_wrapper.c. This subsequently results in copying a large string.
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Analysis
by VulDB Data Team • 06/18/2024
The vulnerability identified as CVE-2018-7584 represents a critical stack-based buffer under-read condition affecting multiple versions of the PHP scripting language. This flaw exists within the php_stream_url_wrap_http_ex function located in the ext/standard/http_fopen_wrapper.c source file, which processes HTTP responses during web requests. The issue manifests when PHP handles HTTP response parsing, creating a scenario where memory is accessed beyond its allocated boundaries. The under-read condition occurs during the processing of HTTP responses, particularly when the system attempts to copy a large string into memory that has been improperly managed. This vulnerability falls under the Common Weakness Enumeration category CWE-126, which specifically addresses "Buffer Under-read" conditions where programs access memory locations before the beginning of a buffer. The flaw demonstrates characteristics consistent with CWE-125, "Out-of-bounds Read", as the program attempts to read data from memory locations that are outside the bounds of the allocated buffer space. The vulnerability is particularly dangerous because it occurs during HTTP response handling, which is a fundamental operation in web applications, making it exploitable in various attack scenarios.
The operational impact of this vulnerability extends across multiple PHP version streams, affecting PHP 5.6 through 5.6.33, 7.0.x versions prior to 7.0.28, 7.1.x versions through 7.1.14, and 7.2.x versions through 7.2.2. When exploited, the buffer under-read can lead to information disclosure, application crashes, or potentially remote code execution depending on the specific system configuration and attack vector. The vulnerability's exploitation requires an attacker to craft a malicious HTTP response that triggers the specific parsing path where the under-read occurs. This typically happens when PHP applications use functions that fetch remote content through HTTP, such as file_get_contents, curl, or similar functions that internally utilize the vulnerable http_fopen_wrapper. The under-read condition can expose sensitive data from adjacent memory locations, potentially revealing stack contents, heap data, or other application information that could aid in further exploitation attempts. The vulnerability demonstrates characteristics aligned with the attack pattern described in the MITRE ATT&CK framework under T1059, "Command and Scripting Interpreter", where attackers may leverage such memory corruption flaws to execute arbitrary code or gain unauthorized access to systems. The impact is particularly severe in web applications where user input directly influences HTTP request handling, creating potential for server-side request forgery or remote code execution attacks.
Mitigation strategies for CVE-2018-7584 focus primarily on upgrading affected PHP installations to patched versions that address the buffer under-read condition in the HTTP response parsing logic. System administrators should immediately apply security patches released by the PHP development team, ensuring that all affected PHP versions are updated to their respective secure releases. Additionally, implementing network-level restrictions can help reduce exposure by limiting access to external HTTP resources or by employing proxy servers that filter and validate HTTP responses before they reach the PHP application. The implementation of proper input validation and sanitization within PHP applications can provide additional defense-in-depth measures, though these should not be considered primary mitigations. Organizations should also consider implementing intrusion detection systems that monitor for suspicious HTTP request patterns that might indicate exploitation attempts. Security monitoring should include tracking for application crashes or unexpected behavior that could indicate the exploitation of memory corruption vulnerabilities. The patching process should be carefully managed to ensure compatibility with existing applications, as PHP updates may introduce breaking changes that require code modifications. Regular security audits and vulnerability assessments should be conducted to identify other potential memory corruption issues within the application stack, particularly focusing on functions that handle external data processing and network communications. Organizations should also implement proper application hardening measures, including stack canaries, address space layout randomization, and other exploit mitigations that make successful exploitation more difficult even if the underlying vulnerability remains unpatched.