CVE-2015-8878 in PHP
Summary
by MITRE
main/php_open_temporary_file.c in PHP before 5.5.28 and 5.6.x before 5.6.12 does not ensure thread safety, which allows remote attackers to cause a denial of service (race condition and heap memory corruption) by leveraging an application that performs many temporary-file accesses.
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Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2015-8878 represents a critical thread safety issue within PHP's temporary file handling mechanism, specifically in the php_open_temporary_file.c component. This flaw exists in PHP versions prior to 5.5.28 and 5.6.12, affecting a significant portion of web applications that rely on PHP for server-side processing. The vulnerability stems from inadequate synchronization mechanisms during temporary file creation and access operations, creating a race condition scenario that can be exploited remotely by attackers.
The technical implementation of this vulnerability involves the improper handling of temporary file operations in a multi-threaded environment where multiple processes or threads may simultaneously attempt to create or access temporary files. When PHP applications perform frequent temporary file operations, the lack of proper thread synchronization allows concurrent access patterns that can result in heap memory corruption. This occurs because the temporary file creation logic does not properly serialize access to shared resources, leading to situations where multiple threads might attempt to write to or modify the same memory locations simultaneously. The race condition manifests when one thread is in the process of creating a temporary file while another thread attempts to access or modify the same file or related memory structures, causing unpredictable behavior and potential system crashes.
The operational impact of CVE-2015-8878 extends beyond simple denial of service conditions to encompass potential heap memory corruption that can lead to more severe consequences. Attackers can leverage this vulnerability to cause application instability, system crashes, or even potentially execute arbitrary code depending on the specific environment and application configuration. The vulnerability is particularly dangerous in web server environments where PHP applications handle concurrent requests from multiple clients, as the race condition can be triggered through normal application operation patterns. This makes the vulnerability highly exploitable in production environments where PHP applications are subjected to high traffic loads and frequent temporary file operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-362, which describes a race condition flaw in software design, and can be categorized under ATT&CK technique T1499.200 for resource hijacking through denial of service. The vulnerability demonstrates how seemingly minor implementation details in core system components can create significant security risks when operating in concurrent environments. Organizations should prioritize patching this vulnerability by upgrading to PHP versions 5.5.28 or later, or 5.6.12 and later, as these releases contain the necessary thread safety improvements. Additionally, system administrators should monitor application behavior for signs of temporary file access patterns that might exacerbate the vulnerability, and consider implementing additional application-level protections such as proper error handling and resource cleanup routines to minimize potential exploitation impact.