CVE-2019-19636 in libsixel
Summary
by MITRE
An issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_encode_body at tosixel.c.
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Analysis
by VulDB Data Team • 03/09/2024
The vulnerability identified as CVE-2019-19636 represents a critical integer overflow flaw within the libsixel library version 1.8.2, specifically within the sixel_encode_body function located in the tosixel.c source file. This library serves as a conversion utility for transforming bitmap images into sixel format, commonly used for terminal-based image display in legacy systems and certain modern terminal emulators. The integer overflow occurs during the processing of image data where the function fails to properly validate or handle large integer values that exceed the bounds of their designated data types, creating potential for arbitrary code execution or system instability.
The technical nature of this vulnerability stems from inadequate input validation and boundary checking within the image encoding process. When processing certain image dimensions or data structures, the sixel_encode_body function performs calculations that can result in integer overflow conditions, where the result exceeds the maximum value that can be represented by the target integer type. This overflow can lead to unexpected behavior in memory allocation, buffer handling, or loop control structures, potentially allowing attackers to manipulate program execution flow or corrupt memory regions. The flaw is particularly dangerous because it occurs during the image encoding phase, which means any application using libsixel for image processing could be vulnerable to exploitation through maliciously crafted input files.
The operational impact of this vulnerability extends across various systems that utilize libsixel for terminal-based image rendering, including but not limited to terminal emulators, image processing applications, and legacy system interfaces that depend on sixel graphics capabilities. Attackers could potentially leverage this vulnerability through crafted image files or data streams that trigger the overflow condition when processed by vulnerable applications. The exploitation could result in denial of service conditions, arbitrary code execution, or information disclosure depending on the specific implementation details and system configuration. Given the widespread use of sixel encoding in terminal-based environments and the potential for remote exploitation through image processing pipelines, this vulnerability poses significant risk to both individual systems and networked environments.
Mitigation strategies for CVE-2019-19636 should prioritize immediate patching of the libsixel library to version 1.8.3 or later, which contains the necessary fixes for the integer overflow condition. System administrators should conduct comprehensive inventory assessments to identify all applications and services utilizing libsixel, particularly those handling untrusted image data. Additional defensive measures include implementing strict input validation and sanitization for image processing pipelines, deploying network segmentation to limit exposure, and monitoring for suspicious image file processing activities. From a cybersecurity framework perspective, this vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and could potentially map to ATT&CK techniques involving code injection and privilege escalation through memory corruption exploits. Organizations should also consider implementing automated vulnerability scanning tools to detect other potential integer overflow conditions within their software dependencies and maintain updated threat intelligence feeds to monitor for related exploitation attempts.