CVE-2020-18428 in tinyexr
Summary
by MITRE • 07/27/2021
tinyexr commit 0.9.5 was discovered to contain an array index error in the tinyexr::SaveEXR component, which can lead to a denial of service (DOS).
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Analysis
by VulDB Data Team • 08/05/2021
The vulnerability identified as CVE-2020-18428 resides within the tinyexr library version 0.9.5, specifically within the tinyexr::SaveEXR component that handles the saving of EXR (OpenEXR) image files. This library is widely used in computer graphics applications, rendering engines, and image processing software due to its efficient handling of high dynamic range images. The flaw manifests as an array index error that occurs during the serialization process when the library attempts to write EXR file data to disk.
The technical nature of this vulnerability stems from inadequate input validation and boundary checking within the SaveEXR function. When processing certain malformed or specially crafted EXR data structures, the library fails to properly validate array indices before accessing memory locations, leading to out-of-bounds memory access patterns. This type of error falls under the CWE-129 vulnerability category, which specifically addresses insufficient bound checking in array indexing operations. The flaw represents a classic buffer overflow condition that can be triggered through improper input handling during file serialization.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially be exploited to cause application crashes or system instability. Attackers who can influence the input data processed by the tinyexr library may be able to craft malicious EXR files that trigger the array index error, resulting in application termination or system resource exhaustion. This makes the vulnerability particularly dangerous in environments where the library processes untrusted input data from external sources, such as web applications, content management systems, or collaborative rendering platforms. The vulnerability aligns with ATT&CK technique T1499.004, which covers the use of resource exhaustion to cause denial of service.
Mitigation strategies for this vulnerability require immediate patching of the affected tinyexr library to version 0.9.6 or later, which contains the necessary fixes for the array index error. System administrators should implement input validation measures to sanitize all EXR file data before processing, particularly when handling external or untrusted inputs. Additionally, deploying network segmentation and access controls can help limit the potential impact of exploitation attempts. Organizations should also consider implementing application whitelisting policies and monitoring for unusual application behavior that might indicate exploitation attempts. The fix typically involves adding proper array boundary checks and input validation routines to prevent the out-of-bounds memory access that leads to the denial of service condition.