CVE-2004-0421 in libpng
Summary
by MITRE
The Portable Network Graphics library (libpng) 1.0.15 and earlier allows attackers to cause a denial of service (crash) via a malformed PNG image file that triggers an error that causes an out-of-bounds read when creating the error message.
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Analysis
by VulDB Data Team • 06/28/2019
The vulnerability identified as CVE-2004-0421 affects the Portable Network Graphics library version 1.0.15 and earlier implementations, representing a critical security flaw that can be exploited to cause denial of service conditions. This issue specifically targets the error handling mechanism within libpng, which is a widely-used open-source library for processing png image files across numerous operating systems and applications. The vulnerability arises from inadequate input validation when processing malformed png image files, creating a scenario where legitimate error conditions trigger unexpected behavior in the library's memory management.
The technical flaw manifests as an out-of-bounds read condition that occurs during the construction of error messages when libpng encounters corrupted or malformed png data. This particular vulnerability falls under the CWE-125 Out-of-bounds Read classification, which represents a fundamental memory safety issue where an application attempts to read data from memory locations outside the bounds of allocated buffers. The error handling code path within libpng does not properly validate the boundaries of memory access when generating error messages, allowing attackers to craft specially crafted png files that trigger this condition. When such malformed images are processed by vulnerable applications, the out-of-bounds read causes memory corruption that ultimately leads to application crashes and system instability.
The operational impact of this vulnerability extends far beyond simple denial of service, as it affects countless applications and systems that depend on libpng for image processing functionality. Any software application that utilizes libpng version 1.0.15 or earlier for handling png image files becomes a potential target for exploitation, including web browsers, image viewers, graphic design applications, and server applications that process user-uploaded content. This vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service and represents a classic example of how seemingly benign input validation failures can lead to system-wide stability issues. The attack vector is particularly concerning because it requires minimal technical expertise to craft malicious png files that can cause widespread disruption across multiple platforms and applications that rely on the affected library.
The mitigation strategy for CVE-2004-0421 involves immediate upgrading of libpng installations to version 1.0.16 or later, which contains the necessary patches to address the out-of-bounds read condition in error handling code. System administrators should prioritize patching all affected systems and applications that utilize libpng, particularly those handling untrusted image data from external sources. Additionally, implementing proper input validation and sanitization measures at application layers can provide defense-in-depth protection against similar vulnerabilities. Organizations should also consider deploying network monitoring solutions to detect and block potentially malicious png files in transit, while maintaining comprehensive logging of image processing activities to identify any exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date third-party libraries and implementing robust security practices in software development lifecycle processes to prevent such memory safety issues from compromising system integrity and availability.