CVE-2018-8976 in Exiv2
Summary
by MITRE
In Exiv2 0.26, jpgimage.cpp allows remote attackers to cause a denial of service (image.cpp Exiv2::Internal::stringFormat out-of-bounds read) via a crafted file.
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Analysis
by VulDB Data Team • 02/24/2023
The vulnerability identified as CVE-2018-8976 represents a critical out-of-bounds read flaw within the Exiv2 image processing library version 0.26. This issue specifically affects the handling of jpeg image files through the jpgimage.cpp component, which is part of the broader Exiv2 framework used for reading and writing image metadata. The flaw occurs during the processing of malformed jpeg files that contain crafted data structures designed to trigger memory access violations. This vulnerability falls under the Common Weakness Enumeration category CWE-125, which describes out-of-bounds read conditions where a program accesses memory beyond the boundaries of a buffer, potentially leading to unpredictable behavior and system instability.
The technical execution of this vulnerability involves the Exiv2::Internal::stringFormat function within the image.cpp file, which processes formatted strings during jpeg metadata parsing. When a remote attacker submits a specially crafted jpeg file, the library's string formatting routine attempts to read memory locations that are outside the valid bounds of allocated buffers. This out-of-bounds memory access can result in segmentation faults, application crashes, or in some cases, may provide opportunities for more sophisticated exploitation techniques. The vulnerability is particularly concerning because it can be triggered remotely through web applications or services that process user-uploaded jpeg images without proper validation, making it a significant threat to web-based image processing systems.
The operational impact of CVE-2018-8976 extends beyond simple denial of service conditions, as it can affect any system or application that relies on Exiv2 for image metadata processing. Web applications, content management systems, digital asset management platforms, and image processing services that accept user uploads are all at risk. The vulnerability can be exploited in scenarios where attackers upload malicious jpeg files to trigger crashes in image processing pipelines, potentially causing service disruption or creating opportunities for further attacks. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1203, which involves the use of malicious files to cause system instability or resource exhaustion, and could be leveraged as part of broader attack chains targeting web applications or file processing services.
Mitigation strategies for CVE-2018-8976 should prioritize immediate patching of Exiv2 library installations to version 0.27 or later, where the vulnerability has been addressed through improved bounds checking and input validation mechanisms. System administrators should implement strict file validation protocols, including MIME type checking and file format verification, before processing any uploaded images. Additionally, deploying intrusion detection systems that monitor for unusual file processing patterns and implementing sandboxing techniques for image processing operations can help contain potential exploitation attempts. Organizations should also consider implementing automated vulnerability scanning tools that can detect and prevent the execution of known malicious image files. The fix implemented in Exiv2 0.27 specifically addresses the out-of-bounds read by enhancing the string formatting function with proper buffer boundary checks and robust error handling, preventing the memory access violations that previously enabled denial of service conditions.