CVE-2019-19638 in libsixel
Summary
by MITRE
An issue was discovered in libsixel 1.8.2. There is a heap-based buffer overflow in the function load_pnm at frompnm.c, due to an integer overflow.
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Analysis
by VulDB Data Team • 03/09/2024
The vulnerability identified as CVE-2019-19638 represents a critical heap-based buffer overflow in the libsixel library version 1.8.2, specifically within the load_pnm function located in the frompnm.c source file. This issue arises from an integer overflow condition that occurs during the processing of PNM (Portable AnyMap) image format files, which are commonly used for storing raster graphics data. The libsixel library serves as a conversion tool for transforming image data into sixel graphics format, which is particularly relevant for terminal-based image display in legacy systems and specialized applications. The vulnerability manifests when the library attempts to allocate memory for image data processing, where an integer overflow corrupts the memory allocation calculations, leading to potential memory corruption that can be exploited by malicious actors.
The technical flaw stems from improper input validation and arithmetic handling within the load_pnm function, where the library fails to adequately check for integer overflow conditions before performing memory allocation operations. When processing malformed or specially crafted PNM files, the integer overflow causes the calculated buffer size to wrap around to a small value, while the actual memory allocation attempts to reserve space based on the overflowed value. This discrepancy creates a situation where the program allocates insufficient memory for the intended data, resulting in heap corruption when the application attempts to write beyond the allocated buffer boundaries. The vulnerability is classified as a heap-based buffer overflow, which is particularly dangerous because it can be leveraged for arbitrary code execution or denial of service attacks, as the corrupted memory can be manipulated to redirect program execution flow or cause application crashes.
The operational impact of this vulnerability extends across various systems that utilize libsixel for image processing, particularly in terminal-based environments, legacy systems, and applications that handle image file conversions. Attackers could exploit this vulnerability by crafting malicious PNM files that trigger the integer overflow condition during the loading process, potentially leading to remote code execution on systems that process such files automatically. The vulnerability affects not only individual user systems but also server applications and automated processing pipelines that depend on libsixel for image conversion tasks. The exploitation of this flaw could result in complete system compromise, data corruption, or service disruption, making it a significant concern for organizations maintaining systems that process untrusted image data. Security researchers have categorized this issue under CWE-190, which specifically addresses integer overflow conditions, and it aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation and system compromise.
Mitigation strategies for CVE-2019-19638 should prioritize immediate patching of affected systems with the latest version of libsixel that addresses the integer overflow condition in the load_pnm function. Organizations should implement strict input validation and sanitization for all image file processing, particularly when handling untrusted data sources. Network segmentation and access controls should be enforced to limit exposure of systems that process image files, while monitoring systems should be configured to detect anomalous file processing behavior that might indicate exploitation attempts. Additionally, application developers should consider implementing defensive programming practices such as bounds checking, explicit integer overflow detection, and proper memory allocation validation. Regular security assessments and vulnerability scanning should be conducted to identify systems running outdated versions of libsixel, and automated patch management systems should be deployed to ensure timely remediation across enterprise environments. The vulnerability also underscores the importance of maintaining up-to-date software libraries and implementing robust software supply chain security measures to prevent the deployment of vulnerable components in production environments.