CVE-2018-14883 in PHP
Summary
by MITRE
An issue was discovered in PHP before 5.6.37, 7.0.x before 7.0.31, 7.1.x before 7.1.20, and 7.2.x before 7.2.8. An Integer Overflow leads to a heap-based buffer over-read in exif_thumbnail_extract of exif.c.
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Analysis
by VulDB Data Team • 04/29/2023
The vulnerability identified as CVE-2018-14883 represents a critical integer overflow condition that affects multiple versions of the PHP programming language across its 5.6, 7.0, 7.1, and 7.2 release lines. This issue specifically resides within the exif_thumbnail_extract function located in the exif.c source file, which processes EXIF metadata from image files. The integer overflow occurs when processing thumbnail data embedded within image files, creating a scenario where a maliciously crafted image file can trigger unexpected behavior in the PHP runtime environment.
The technical flaw manifests as an integer overflow that subsequently leads to a heap-based buffer over-read condition. When PHP processes an image file containing EXIF thumbnail data, the application calculates certain buffer sizes based on integer values that can exceed the maximum representable value for the data type used. This overflow causes the application to allocate insufficient memory for the buffer, but when the code attempts to read beyond the allocated boundaries, it accesses memory that may contain arbitrary data or be unmapped. The vulnerability is classified under CWE-190 as an integer overflow condition, specifically involving signed integer overflow that results in an underflow or wraparound behavior.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it creates potential for remote code execution under certain conditions. Attackers can craft malicious image files that, when processed by a vulnerable PHP application, cause the application to read beyond allocated memory boundaries. This behavior can lead to information disclosure, application crashes, or potentially allow attackers to execute arbitrary code on the affected system. The vulnerability is particularly dangerous in web applications that process user-uploaded images, as it provides an attack vector through file upload handlers that utilize PHP's EXIF processing capabilities.
Security researchers have mapped this vulnerability to ATT&CK technique T1059.007, which involves the use of scripting languages for execution, as the exploitation may involve manipulation of PHP scripts that process image uploads. The vulnerability affects PHP applications that utilize the exif_read_data function or related EXIF processing functions, making it prevalent in content management systems, image galleries, and any web applications that handle image file processing. Organizations running vulnerable PHP versions are at risk of exploitation through web-based attacks targeting image upload functionality, particularly in applications that do not properly validate or sanitize uploaded image files before processing them with PHP's EXIF functions.
The recommended mitigation strategy involves immediate upgrade of affected PHP installations to versions that contain the patch for this vulnerability, specifically PHP 5.6.37, 7.0.31, 7.1.20, and 7.2.8 or later. Additionally, administrators should implement proper input validation and sanitization measures for image uploads, including file type checking, size limitations, and consideration of using alternative image processing libraries that do not rely on vulnerable EXIF parsing functions. Network-based mitigations such as web application firewalls can provide additional protection, though the most effective defense remains the immediate patching of vulnerable systems to prevent exploitation of this heap-based buffer over-read condition.