CVE-2015-7700 in pngcrush
Summary
by MITRE
Double-free vulnerability in the sPLT chunk structure and png.c in pngcrush before 1.7.87 allows attackers to have unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 11/12/2019
The CVE-2015-7700 vulnerability represents a critical double-free memory corruption issue discovered in pngcrush version 1.7.87 and earlier. This vulnerability specifically affects the handling of sPLT chunk structures within PNG image files, demonstrating a classic memory safety flaw that can lead to arbitrary code execution or system compromise. The vulnerability exists in the png.c file which processes PNG image data, making it particularly dangerous as it can be exploited through malformed image files processed by vulnerable software applications. The double-free condition occurs when the same memory block is freed twice during the processing of PNG files, potentially allowing attackers to manipulate the heap memory structure and execute malicious code.
The technical flaw stems from improper memory management within the pngcrush library when processing sPLT (suggested palette) chunks in PNG files. When the software encounters a malformed sPLT chunk structure, it fails to properly validate the chunk data before attempting to free allocated memory resources. This oversight creates a scenario where the same memory address gets referenced multiple times during the cleanup process, leading to a double-free condition that can be exploited by attackers. The vulnerability is particularly insidious because it operates at the memory management level, making it difficult to detect through conventional security scanning methods. The unspecified impact mentioned in the description indicates that the consequences can vary significantly depending on the execution environment and memory layout, potentially resulting in denial of service, information disclosure, or complete system compromise.
The operational impact of CVE-2015-7700 extends far beyond simple image processing applications, as pngcrush is widely used in various image manipulation workflows including web applications, content management systems, and automated image processing pipelines. Attackers can exploit this vulnerability by crafting malicious PNG files containing specially constructed sPLT chunks that trigger the double-free condition when processed by vulnerable versions of pngcrush. The vulnerability affects not only direct usage of pngcrush but also any software that incorporates the vulnerable library, creating a broad attack surface across multiple applications and systems. This type of vulnerability is particularly dangerous in automated environments where image files are processed without manual review, as attackers can silently compromise systems through seemingly benign image uploads.
Mitigation strategies for CVE-2015-7700 primarily focus on upgrading to pngcrush version 1.7.87 or later, which contains the necessary patches to address the double-free condition in sPLT chunk processing. Organizations should implement comprehensive patch management procedures to ensure all systems using pngcrush or affected libraries are updated promptly. Additionally, input validation and sanitization measures should be implemented at the application level to reject malformed PNG files before they reach the vulnerable processing code. Security professionals should consider implementing sandboxing techniques when processing untrusted image files, as recommended by the CWE-459 standard for incomplete cleanup vulnerabilities. The ATT&CK framework categorizes this type of vulnerability under the T1059.007 technique for exploitation of memory corruption vulnerabilities, emphasizing the need for robust memory safety practices and regular security assessments to prevent exploitation. Organizations should also consider implementing network segmentation and monitoring to detect potential exploitation attempts targeting this vulnerability in their environments.