CVE-2018-7728 in Exempi
Summary
by MITRE
An issue was discovered in Exempi through 2.4.4. XMPFiles/source/FileHandlers/TIFF_Handler.cpp mishandles a case of a zero length, leading to a heap-based buffer over-read in the MD5Update() function in third-party/zuid/interfaces/MD5.cpp.
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Analysis
by VulDB Data Team • 02/17/2023
The vulnerability CVE-2018-7728 represents a critical heap-based buffer over-read issue within the Exempi library version 2.4.4 and earlier. This flaw resides in the TIFF_Handler.cpp file within the XMPFiles component, specifically in how it processes certain TIFF image files with zero-length data segments. The vulnerability manifests when the library encounters a malformed TIFF structure where a particular data element has a zero length, creating a scenario that leads to improper memory handling during the processing of metadata within these image files. The issue stems from inadequate input validation and boundary checking within the file handling logic, allowing maliciously crafted TIFF files to trigger unexpected memory access patterns.
The technical exploitation of this vulnerability occurs through the MD5Update() function located in third-party/zuid/interfaces/MD5.cpp, which is called during the processing of the malformed TIFF data. When the TIFF handler encounters the zero-length element, it fails to properly validate the data boundaries before attempting to process the MD5 checksum calculation. This results in a buffer over-read condition where the MD5Update() function attempts to read beyond the allocated memory boundaries, potentially accessing uninitialized or adjacent memory regions. The flaw is classified as a heap-based buffer over-read because the memory corruption occurs in heap-allocated memory regions rather than stack memory, making it particularly challenging to detect and exploit reliably.
From an operational perspective, this vulnerability presents significant security implications for systems that process TIFF image files through the Exempi library. Attackers could leverage this issue by crafting specially formatted TIFF files that trigger the buffer over-read condition, potentially leading to information disclosure, application crashes, or in some cases, arbitrary code execution depending on the system's memory layout and the specific exploitation context. The vulnerability affects any application or service that relies on Exempi for processing XMP metadata within TIFF files, including digital asset management systems, image processing pipelines, and content management platforms. The impact is particularly concerning in server environments where automated processing of user-uploaded files occurs without proper sanitization.
The vulnerability aligns with CWE-125, which describes "Out-of-bounds Read" conditions in software implementations, and specifically relates to improper input validation and memory boundary checking. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain under techniques such as T1059 for code execution or T1068 for privilege escalation, depending on the exploitation context and target environment. The vulnerability also maps to T1203, which involves the exploitation of memory corruption vulnerabilities to gain unauthorized access or execute malicious code. Organizations should consider implementing input validation measures, regular library updates, and proper sandboxing mechanisms to mitigate the risk of exploitation. Additionally, the vulnerability highlights the importance of proper error handling and boundary checking in third-party library integrations, as the issue originated from a function within a third-party component rather than the core library functionality.
Mitigation strategies should include immediate patching of the Exempi library to version 2.4.5 or later, where the buffer over-read issue has been addressed through improved boundary checking and input validation. System administrators should implement proper file validation mechanisms before processing TIFF files, including signature verification and size limitations for metadata elements. Network segmentation and application whitelisting can help limit the potential impact if exploitation occurs. Regular security assessments should include verification of third-party library versions and their known vulnerabilities. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date software dependencies and implementing comprehensive input validation across all file processing pipelines to prevent similar memory corruption issues from compromising system security.