CVE-2016-8696 in potrace
Summary
by MITRE
The bm_readbody_bmp function in bitmap_io.c in potrace before 1.13 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a crafted BMP image, a different vulnerability than CVE-2016-8694 and CVE-2016-8695.
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2016-8696 affects the potrace library version 1.13 and earlier, specifically within the bitmap_io.c file in the bm_readbody_bmp function. This issue represents a denial of service vulnerability that can be exploited by remote attackers through the manipulation of BMP image files. The flaw manifests as a NULL pointer dereference condition that ultimately leads to application crash, disrupting normal service operations. Unlike related vulnerabilities CVE-2016-8694 and CVE-2016-8695, this particular vulnerability presents distinct characteristics in its exploitation methodology and impact vector.
The technical implementation of this vulnerability stems from inadequate input validation within the bitmap image parsing routine. When the bm_readbody_bmp function processes a malformed BMP image file, it fails to properly handle certain edge cases in the image header or data structure, resulting in a scenario where a NULL pointer is dereferenced during the parsing process. This occurs because the function does not sufficiently validate the integrity of the BMP file format before attempting to access memory locations that may not have been properly initialized or allocated. The vulnerability falls under the category of improper input validation and memory safety issues, aligning with CWE-476 which specifically addresses NULL pointer dereference conditions. The attack surface is particularly concerning as it allows remote exploitation through image processing operations that are commonly encountered in web applications and document handling systems.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable more sophisticated attack vectors. When exploited, the NULL pointer dereference causes the potrace library to crash, which can result in complete application termination or system instability if the library is used in critical infrastructure components. This type of denial of service vulnerability can be particularly damaging in environments where image processing services are essential for business operations, such as content management systems, document conversion services, or web applications that handle user-uploaded images. The vulnerability demonstrates how seemingly benign file format processing can become a critical security concern when proper input validation and error handling mechanisms are absent. From an attacker perspective, this represents a low-effort method to disrupt services, requiring only the creation of a malicious BMP file to trigger the crash condition.
Mitigation strategies for CVE-2016-8696 should focus on both immediate patching and defensive programming practices. The primary remediation involves upgrading to potrace version 1.13 or later, where the vulnerability has been addressed through improved input validation and error handling mechanisms. Organizations should implement comprehensive testing procedures to verify that updated libraries properly handle malformed BMP files without crashing. Additionally, defensive programming measures should be adopted including input sanitization, proper error handling, and implementing timeouts for image processing operations to prevent resource exhaustion attacks. Security practitioners should also consider implementing network-based intrusion detection systems to monitor for suspicious image file uploads and establish proper access controls to limit exposure. The vulnerability underscores the importance of following secure coding practices and adheres to ATT&CK technique T1499 which covers network denial of service attacks, emphasizing the need for robust error handling in file processing components. Organizations utilizing potrace or similar libraries should conduct thorough security assessments to identify other potential vulnerabilities in their image processing pipelines and ensure comprehensive protection against similar classes of flaws.