CVE-2013-4636 in PHP
Summary
by MITRE
The mget function in libmagic/softmagic.c in the Fileinfo component in PHP 5.4.x before 5.4.16 allows remote attackers to cause a denial of service (invalid pointer dereference and application crash) via an MP3 file that triggers incorrect MIME type detection during access to an finfo object.
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Analysis
by VulDB Data Team • 12/20/2024
The vulnerability described in CVE-2013-4636 represents a critical denial of service flaw within PHP's Fileinfo component that specifically affects versions 5.4.x prior to 5.4.16. This issue manifests through the mget function located in libmagic/softmagic.c, which is responsible for MIME type detection when processing file information through finfo objects. The flaw occurs during the analysis of MP3 files, where the software's handling of certain malformed or specially crafted audio files triggers an invalid pointer dereference that ultimately leads to application crash.
The technical exploitation of this vulnerability involves the manipulation of MP3 file structures to create conditions where the libmagic library's softmagic.c component fails to properly validate file headers during MIME type detection. When PHP's finfo object attempts to analyze such malicious MP3 files, the mget function encounters corrupted or unexpected data patterns that cause it to dereference invalid memory pointers. This memory access violation results in immediate application termination and prevents further processing of legitimate file requests. The vulnerability falls under the category of improper input validation and memory safety issues, aligning with CWE-476 which addresses null pointer dereference conditions.
From an operational impact perspective, this vulnerability presents a significant risk to web applications that rely on PHP's Fileinfo functionality for file type detection and validation. Attackers can leverage this flaw to perform denial of service attacks against PHP-based web servers, potentially disrupting services for legitimate users. The impact extends beyond simple service interruption as the vulnerability can be exploited through web interfaces where users upload or submit files, making it particularly dangerous in content management systems, file upload handlers, and any application that performs automatic MIME type detection on user-submitted content. The vulnerability demonstrates how seemingly benign file processing operations can become attack vectors when proper input validation and error handling are absent.
The mitigation strategy for CVE-2013-4636 centers on upgrading PHP installations to version 5.4.16 or later, which contains the necessary patches to address the invalid pointer dereference issue. Organizations should also implement additional defensive measures such as input sanitization and file validation before processing user uploads, though the primary solution remains the software update. Security teams should monitor for similar patterns in other file processing libraries and consider implementing application-level restrictions on file types that can be processed through finfo objects. The vulnerability serves as a reminder of the importance of memory safety in file handling operations and demonstrates how the ATT&CK framework's technique T1499.004 for network denial of service can be achieved through application-level flaws in file processing components.