CVE-2016-7128 in PHP
Summary
by MITRE
The exif_process_IFD_in_TIFF function in ext/exif/exif.c in PHP before 5.6.25 and 7.x before 7.0.10 mishandles the case of a thumbnail offset that exceeds the file size, which allows remote attackers to obtain sensitive information from process memory via a crafted TIFF image.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-7128 represents a critical information disclosure flaw within PHP's exif extension, specifically affecting versions prior to 5.6.25 and 7.0.10. This issue resides in the exif_process_IFD_in_TIFF function located in the ext/exif/exif.c source file, where improper handling of thumbnail offset values creates a pathway for malicious actors to extract sensitive data from process memory. The flaw occurs when a crafted TIFF image contains a thumbnail offset that extends beyond the actual file boundaries, enabling attackers to perform out-of-bounds memory reads that reveal confidential information.
The technical exploitation of this vulnerability stems from inadequate bounds checking within the TIFF parsing logic. When PHP processes a TIFF image through the exif extension, it attempts to locate and extract thumbnail data based on offset values specified in the image metadata. However, the implementation fails to validate whether these offset values remain within the confines of the actual file size, allowing for arbitrary memory access patterns. This memory corruption vulnerability operates under CWE-125, which classifies it as an out-of-bounds read condition, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage in exploitation contexts. The flaw demonstrates characteristics of improper input validation where the system does not adequately verify the legitimacy of metadata offsets before attempting to access memory locations.
The operational impact of CVE-2016-7128 extends beyond simple information disclosure, as the extracted memory contents may contain sensitive data including database credentials, session tokens, application secrets, or other confidential information that could be leveraged for further attacks. Attackers can craft malicious TIFF files that trigger this vulnerability when processed by vulnerable PHP applications, particularly those handling user-uploaded images or serving image content through web applications. This vulnerability is particularly dangerous in web environments where PHP processes user-generated content, as it allows remote attackers to systematically extract memory contents without requiring any special privileges or authentication. The attack surface includes any PHP application that utilizes the exif extension for image processing, making it a widespread concern across numerous web applications and content management systems.
Mitigation strategies for this vulnerability primarily focus on immediate version upgrades to PHP 5.6.25 or 7.0.10 and later releases where the flaw has been addressed through proper bounds checking implementation. Organizations should also implement additional defensive measures including input validation for image uploads, sandboxing of image processing operations, and monitoring for unusual memory access patterns in web application logs. The fix implemented by PHP developers involved strengthening the validation logic to ensure that thumbnail offset values do not exceed file boundaries before attempting to access memory locations, thereby preventing the out-of-bounds read conditions that enabled information disclosure. Security teams should also consider implementing web application firewalls with content inspection capabilities to detect and block malicious TIFF files attempting to exploit this vulnerability, while maintaining regular security assessments to identify similar issues within other image processing libraries and components.