CVE-2006-5793 in libpng
Summary
by MITRE
The sPLT chunk handling code (png_set_sPLT function in pngset.c) in libpng 1.0.6 through 1.2.12 uses a sizeof operator on the wrong data type, which allows context-dependent attackers to cause a denial of service (crash) via malformed sPLT chunks that trigger an out-of-bounds read.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 04/27/2026
The vulnerability described in CVE-2006-5793 represents a critical memory safety issue within the libpng library version 1.0.6 through 1.2.12. This flaw specifically affects the handling of sPLT chunks in png_set_sPLT function located in pngset.c file. The root cause stems from improper type handling during memory allocation calculations where the sizeof operator is applied to an incorrect data type. This fundamental programming error creates a scenario where maliciously crafted PNG files containing malformed sPLT chunks can trigger unexpected behavior in the affected software systems.
The technical implementation of this vulnerability occurs when the png_set_sPLT function processes sPLT chunks, which are used to store suggested palettes in PNG image files. During this processing, the code calculates memory requirements using sizeof on a variable that does not match the actual data structure being allocated. This mismatch results in incorrect memory allocation sizing, leading to out-of-bounds memory reads when the code attempts to access memory locations beyond the intended buffer boundaries. The context-dependent nature of this vulnerability means that the attack requires specific conditions to be met, typically involving the presence of specially crafted sPLT chunks within PNG files that are then processed by vulnerable applications.
The operational impact of this vulnerability manifests as a denial of service condition that can cause applications to crash or terminate unexpectedly. When an application processes a PNG file containing malformed sPLT chunks, the incorrect memory calculations trigger memory access violations that result in segmentation faults or similar runtime errors. This crash behavior can be exploited by attackers to disrupt services, particularly in applications that handle user-uploaded images or process external PNG content without proper validation. The vulnerability affects a wide range of software systems that rely on libpng for image processing, including web servers, image viewers, and content management systems.
This vulnerability maps to CWE-121 in the Common Weakness Enumeration catalog, which classifies it as a stack-based buffer overflow due to improper use of memory allocation functions. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks, where adversaries exploit software vulnerabilities to cause system unavailability. The vulnerability demonstrates the importance of proper memory management and type safety in image processing libraries, particularly in handling user-supplied data. Organizations should implement immediate mitigations including updating to patched versions of libpng, implementing input validation for PNG files, and deploying runtime protections to prevent exploitation of such memory safety issues.
The remediation strategy involves upgrading to libpng versions 1.2.13 or later where the memory allocation logic has been corrected to properly handle the sizeof operator on the correct data types. Additionally, application developers should implement proper input validation and sanitization for all image file processing, particularly when dealing with external or user-generated content. Security monitoring should include detection of malformed PNG files and their processing by vulnerable applications. The vulnerability highlights the necessity of thorough code review and testing for memory safety issues in image processing libraries, as these components are frequently targeted due to their exposure to diverse input sources and their critical role in many software applications.