CVE-2019-20205 in libsixel
Summary
by MITRE
libsixel 1.8.4 has an integer overflow in sixel_frame_resize in frame.c.
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Analysis
by VulDB Data Team • 03/19/2024
The vulnerability identified as CVE-2019-20205 affects libsixel version 1.8.4 and represents a critical integer overflow condition within the sixel_frame_resize function located in the frame.c source file. This flaw occurs when processing sixel graphics data, which is a graphics format used primarily for terminal-based image display. The integer overflow manifests during memory allocation operations where the system attempts to calculate and allocate memory space based on user-provided dimensions or parameters. When these parameters exceed the maximum representable value for the integer type used in the calculation, the result wraps around to a much smaller value, leading to insufficient memory allocation that can subsequently trigger memory corruption or arbitrary code execution.
The technical implementation of this vulnerability stems from inadequate input validation and overflow checking within the sixel graphics processing pipeline. The sixel_frame_resize function handles dynamic resizing of graphics frames and performs calculations to determine the appropriate memory allocation size for the frame buffer. When maliciously crafted input data containing oversized dimension values is processed, the integer arithmetic results in an overflow condition that bypasses normal memory allocation checks. This creates a scenario where the application allocates insufficient memory for the intended frame size, potentially allowing attackers to overwrite adjacent memory regions or manipulate the program's execution flow. The vulnerability is particularly concerning because it can be exploited through various attack vectors including malformed sixel image files, network-based data streams, or malicious terminal sessions that process sixel graphics.
From an operational impact perspective, this vulnerability presents significant security risks to systems that utilize libsixel for graphics processing, particularly in terminal-based applications, remote desktop environments, or any software that handles sixel image data. The integer overflow can lead to denial of service conditions where applications crash due to memory corruption, or more critically, allow for arbitrary code execution if proper exploit mitigation techniques are not in place. Systems using vulnerable versions of libsixel in web browsers, terminal emulators, or remote access tools become potential attack vectors for adversaries seeking to compromise endpoints or escalate privileges. The vulnerability affects not only individual applications but also entire ecosystems that depend on sixel graphics support, making it a widespread concern for organizations maintaining terminal-based infrastructure or applications that process external graphics data.
Mitigation strategies for CVE-2019-20205 should prioritize immediate patching of affected libsixel installations to version 1.8.5 or later, which contains the necessary fixes for the integer overflow condition. Organizations should implement comprehensive input validation measures to sanitize all sixel graphics data before processing, including bounds checking on dimension parameters and explicit overflow detection in memory allocation routines. Network segmentation and access controls should be enforced to limit exposure to potentially malicious sixel data streams, particularly in environments where external data processing is required. Security monitoring should include detection of unusual memory allocation patterns or process behavior that might indicate exploitation attempts. The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and represents a classic example of how insufficient integer arithmetic validation can lead to critical security flaws. From an ATT&CK framework perspective, this vulnerability could be leveraged in initial access or privilege escalation phases, particularly when combined with other exploitation techniques targeting terminal-based applications or remote access systems that process sixel graphics data. System administrators should also consider implementing application whitelisting controls to restrict execution of vulnerable software and maintain regular vulnerability scanning to identify other potential integer overflow conditions in similar graphics processing libraries.