CVE-2017-17722 in Exiv2
Summary
by MITRE
In Exiv2 0.26, there is a reachable assertion in the readHeader function in bigtiffimage.cpp, which will lead to a remote denial of service attack via a crafted TIFF file.
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Analysis
by VulDB Data Team • 01/04/2020
The vulnerability identified as CVE-2017-17722 represents a critical denial of service weakness within the Exiv2 image processing library version 0.26. This flaw manifests as a reachable assertion failure within the readHeader function of the bigtiffimage.cpp source file, specifically when processing maliciously crafted TIFF image files. The Exiv2 library serves as a widely-used open-source tool for reading and writing image metadata across various file formats including TIFF, JPEG, and PNG, making it a critical component in numerous applications and systems that handle digital imagery. The vulnerability's remote exploitation potential arises from the library's ability to process TIFF files from untrusted sources, which are commonly encountered in web applications, email systems, and digital asset management platforms where users can upload or download image files.
The technical root cause of this vulnerability stems from inadequate input validation within the TIFF file parsing logic. When the readHeader function encounters a malformed TIFF header structure, particularly one that violates expected format constraints or contains unexpected data sequences, the assertion mechanism triggers a program termination. This assertion failure occurs because the function does not properly handle edge cases or malformed input data that could be intentionally crafted to exploit the library's parsing routines. The assertion itself is designed to catch programming errors during development, but in a production environment where external input is processed, such assertions should not be reachable as they would cause the application to crash. The specific nature of the flaw involves improper bounds checking and validation of TIFF file structure elements, particularly those related to big TIFF format handling where data types and offsets may exceed standard expectations.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader security implications for systems that rely on Exiv2 for image processing tasks. Remote attackers can exploit this weakness by crafting a specially constructed TIFF file that, when processed by any application using the vulnerable Exiv2 library, will trigger the assertion failure and cause the application to terminate unexpectedly. This denial of service scenario affects web applications, content management systems, digital asset servers, and any software that incorporates Exiv2 for metadata extraction or image handling. The vulnerability is particularly concerning in high-availability environments where such crashes could be leveraged for sustained service disruption, and in applications where users can upload images, as attackers could potentially cause cascading failures across multiple processes or services. The exploitability of this vulnerability is relatively straightforward, requiring only the creation of a malformed TIFF file that triggers the specific assertion condition, making it accessible to attackers with minimal technical expertise.
Mitigation strategies for CVE-2017-17722 primarily focus on immediate library updates and defensive programming practices. The most effective solution involves upgrading to Exiv2 version 0.27 or later, where the assertion failure has been addressed through improved input validation and error handling mechanisms. Organizations should conduct comprehensive inventory checks to identify all systems and applications that utilize Exiv2, particularly those handling user-uploaded content or processing external image files. Additionally, implementing proper input sanitization and validation at application layers can provide defense-in-depth measures, ensuring that even if malformed TIFF files reach processing components, they do not trigger assertion failures. This includes implementing timeout mechanisms, resource limits, and proper error recovery procedures that prevent single malformed inputs from causing complete application failures. The vulnerability aligns with CWE-617, which addresses reachable assertions, and relates to ATT&CK technique T1499.004 for network denial of service, highlighting the importance of robust error handling and input validation in preventing such exploitation scenarios. Organizations should also consider implementing network segmentation and access controls to limit exposure of systems that process external image content, while maintaining regular security updates and vulnerability assessments to prevent similar issues from emerging in other components of their digital infrastructure.