CVE-2020-18430 in tinyexr
Summary
by MITRE • 07/27/2021
tinyexr 0.9.5 was discovered to contain an array index error in the tinyexr::DecodeEXRImage component, which can lead to a denial of service (DOS).
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Analysis
by VulDB Data Team • 08/05/2021
The vulnerability CVE-2020-18430 affects the tinyexr library version 0.9.5, specifically within the tinyexr::DecodeEXRImage component that handles decoding of OpenEXR image files. This array index error represents a classic software flaw that can be exploited to cause system instability or complete service disruption. The issue manifests when the library processes malformed or specially crafted EXR files that contain invalid array indices, leading to out-of-bounds memory access patterns. Such vulnerabilities are particularly concerning in image processing libraries that are widely used across various applications and systems for handling high dynamic range imaging formats.
The technical root cause of this vulnerability stems from inadequate input validation and bounds checking within the EXR decoding logic. When the tinyexr::DecodeEXRImage function processes image data, it fails to properly validate array indices against the actual dimensions of allocated memory buffers. This allows an attacker to craft EXR files containing malicious index values that exceed the bounds of allocated arrays, potentially causing memory corruption or segmentation faults. The vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a direct violation of secure coding practices that mandate bounds checking for all array accesses. The flaw can be classified as a buffer over-read or under-read condition depending on the specific implementation details.
From an operational impact perspective, this vulnerability creates significant risk for systems that rely on the tinyexr library for image processing tasks. The denial of service condition can affect web applications, media processing pipelines, and any software that accepts EXR file uploads or processing requests. Attackers can exploit this vulnerability by uploading malicious EXR files that trigger the array index error during decoding, causing applications to crash or become unresponsive. This can result in complete service disruption for users and systems that depend on EXR file handling capabilities. The vulnerability is particularly dangerous in environments where automated processing of user-uploaded content occurs, as it can be leveraged for sustained denial of service attacks. According to ATT&CK framework, this vulnerability maps to T1499.004 which covers network denial of service attacks, and T1595.002 which involves network infiltration through application vulnerabilities.
Mitigation strategies for CVE-2020-18430 should prioritize immediate library updates to version 0.9.6 or later, which contains the necessary patches for the array index validation issues. Organizations should implement input validation measures that sanitize EXR file content before processing, including verifying file headers and dimensions against expected ranges. Additionally, deployment of robust error handling and memory protection mechanisms can help contain the impact of such vulnerabilities by preventing memory corruption from escalating into more serious security issues. System administrators should monitor for suspicious file upload patterns and implement rate limiting for image processing endpoints to reduce the effectiveness of potential denial of service attacks. The vulnerability also highlights the importance of regular security audits and dependency updates in software supply chains, particularly for libraries that handle untrusted input data.