CVE-2015-2331 in PHP
Summary
by MITRE
Integer overflow in the _zip_cdir_new function in zip_dirent.c in libzip 0.11.2 and earlier, as used in the ZIP extension in PHP before 5.4.39, 5.5.x before 5.5.23, and 5.6.x before 5.6.7 and other products, allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a ZIP archive that contains many entries, leading to a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability CVE-2015-2331 represents a critical integer overflow flaw within the libzip library that affects numerous PHP installations and other software systems. This issue stems from improper handling of integer values during the processing of ZIP archive directory entries, specifically within the _zip_cdir_new function located in zip_dirent.c. The flaw occurs when the library attempts to allocate memory for a large number of entries in a ZIP archive, where the integer overflow leads to incorrect memory allocation calculations. When a maliciously crafted ZIP archive contains an excessive number of entries, the integer overflow causes the system to allocate insufficient memory, resulting in heap-based buffer overflows that can be exploited by remote attackers.
The technical exploitation of this vulnerability leverages the inherent weakness in integer arithmetic handling where the number of entries in a ZIP archive exceeds the maximum value that can be represented by the integer data type used in the allocation calculations. This creates a scenario where the intended memory allocation becomes significantly smaller than required, leading to buffer overflow conditions in heap memory. The vulnerability manifests as either a denial of service through application crashes or potentially allows for arbitrary code execution, depending on the specific system configuration and memory layout. This type of vulnerability falls under CWE-190, which specifically addresses integer overflow conditions that can result in buffer overflows, making it a prime target for exploitation in memory corruption attacks.
The operational impact of CVE-2015-2331 extends across multiple software ecosystems, particularly affecting PHP installations where the ZIP extension relies on libzip for archive processing. Systems running PHP versions before 5.4.39, 5.5.x before 5.5.23, and 5.6.x before 5.6.7 remain vulnerable to this attack vector, creating widespread exposure across web applications and server environments. Attackers can craft malicious ZIP archives containing thousands of entries to trigger the integer overflow, causing applications to crash or potentially execute unintended code. The vulnerability is particularly dangerous in web environments where users can upload files, as it allows for remote code execution without requiring authentication or elevated privileges. This makes it a significant concern for web applications, content management systems, and any platform that processes user-uploaded ZIP archives.
Mitigation strategies for CVE-2015-2331 involve immediate patching of affected PHP installations to versions that include fixes for the integer overflow in libzip. Organizations should also implement input validation and sanitization for ZIP file uploads, including limiting the number of entries allowed in archives and implementing size restrictions. Network-based protections can include deploying web application firewalls that detect and block suspicious ZIP file patterns, while system-level mitigations involve memory protection mechanisms such as stack canaries and address space layout randomization. The vulnerability demonstrates the importance of proper integer overflow handling in security-critical libraries and aligns with ATT&CK technique T1059.007 for remote code execution through memory corruption attacks. Regular security audits of third-party libraries and dependencies are essential to prevent similar vulnerabilities from being exploited in production environments, particularly given the widespread use of libzip across various software platforms and the potential for cascading effects when such fundamental library flaws exist.