CVE-2018-17073 in bitmap
Summary
by MITRE
wernsey/bitmap before 2018-08-18 allows a NULL pointer dereference via a 4-bit image.
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Analysis
by VulDB Data Team • 03/24/2020
The vulnerability identified as CVE-2018-17073 affects the wernsey/bitmap library version prior to 2018-08-18 and represents a critical null pointer dereference flaw that occurs when processing 4-bit image data. This issue manifests within the bitmap library's image parsing functionality where improper input validation leads to memory access violations. The vulnerability specifically targets the handling of 4-bit image formats, which are commonly used in various graphics applications and embedded systems where memory efficiency is paramount. The flaw stems from the library's failure to properly validate image header parameters before attempting to dereference pointers, creating a condition where a null pointer is accessed during image processing operations.
The technical implementation of this vulnerability involves the library's bitmap parsing routine that does not adequately check for null pointers in the image data structure when encountering 4-bit format images. When a 4-bit image is processed, the code attempts to access memory locations that have not been properly initialized or allocated, resulting in a segmentation fault or application crash. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations. The flaw demonstrates poor defensive programming practices where the code assumes that certain memory allocations or data structures will always contain valid pointers without proper validation checks.
From an operational perspective, this vulnerability presents significant risks to systems that rely on the wernsey/bitmap library for image processing tasks. Attackers could exploit this weakness by crafting malicious 4-bit image files that trigger the null pointer dereference, potentially causing denial of service conditions or system instability. The impact extends beyond simple crashes as the vulnerability could be leveraged in more sophisticated attacks where the crash behavior might be used to facilitate further exploitation or as part of a larger attack chain. Systems using this library in embedded environments, web applications, or graphics processing pipelines could experience service interruption or complete application failure when encountering malformed 4-bit image data.
The mitigation strategy for CVE-2018-17073 requires immediate patching of the affected wernsey/bitmap library to version 2018-08-18 or later, which includes proper null pointer validation and input sanitization. Organizations should implement comprehensive testing procedures to verify that the patched library correctly handles all image formats including 4-bit images without triggering memory access violations. Additionally, defensive programming practices should be reinforced throughout the codebase to ensure that all pointer accesses are validated before dereferencing. This vulnerability aligns with ATT&CK technique T1203 which involves the exploitation of input validation flaws to cause system instability, and organizations should consider implementing network segmentation and input validation controls to limit potential attack surface. The fix should also include enhanced logging capabilities to detect and alert on malformed image file processing attempts, providing visibility into potential exploitation attempts.