CVE-2020-35511 in pngcheck
Summary
by MITRE • 08/24/2022
A global buffer overflow was discovered in pngcheck function in pngcheck-2.4.0(5 patches applied) via a crafted png file.
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Analysis
by VulDB Data Team • 09/25/2022
The vulnerability identified as CVE-2020-35511 represents a critical global buffer overflow condition within the pngcheck utility version 2.4.0, which has been patched with five additional modifications. This issue arises from insufficient input validation when processing specially crafted png image files, creating a scenario where maliciously constructed image data can trigger memory corruption. The pngcheck utility serves as a command-line tool for validating png image files, making it a common component in automated testing environments and security scanning workflows. When the utility encounters a malformed png file, the buffer overflow occurs during the parsing process, specifically within the pngcheck function that handles image data validation. This vulnerability demonstrates a classic insufficient bound checking flaw that allows attackers to overwrite adjacent memory regions, potentially leading to arbitrary code execution or application crash. The buffer overflow condition affects the global memory space, meaning that the overflow impacts memory locations that persist beyond the scope of a single function call, amplifying the potential impact of exploitation. The vulnerability is particularly concerning because pngcheck is frequently used in automated systems where image validation is performed without proper user intervention, creating opportunities for remote exploitation through malicious image uploads in web applications, file processing pipelines, or security scanning tools.
The technical implementation of this buffer overflow stems from improper handling of image data structures within the pngcheck utility's parsing logic. When processing png files, the utility reads image headers and metadata without adequate bounds checking on array access operations. The specific flaw occurs during the extraction and validation of image properties where fixed-size buffers are populated with data from potentially untrusted sources. This condition falls under the CWE-121 category of stack-based buffer overflow, though in this case it manifests as a global buffer overflow due to the memory layout and access patterns within the application's architecture. The vulnerability is classified as a memory safety issue in the context of the Common Weakness Enumeration framework, where the improper handling of data boundaries leads to unauthorized memory access. The attack surface is expanded by the fact that pngcheck is often integrated into automated workflows, meaning that a single vulnerable image file can trigger the overflow in production environments. The exploitation requires crafting a specific png file structure that causes the parser to write beyond allocated buffer boundaries, which can be achieved through manipulation of image dimensions, color depth specifications, or chunk data structures within the png format. The vulnerability's impact is further amplified by the fact that pngcheck is commonly used in security contexts, making it a potential target for attackers seeking to compromise security scanning infrastructure or automated testing environments.
The operational implications of CVE-2020-35511 extend beyond simple application instability, as the buffer overflow creates potential for remote code execution and system compromise. When exploited, this vulnerability allows attackers to manipulate memory contents in ways that could lead to arbitrary code execution, particularly in environments where pngcheck is executed with elevated privileges or in automated processing pipelines. The vulnerability affects systems running pngcheck version 2.4.0 with the five applied patches, indicating that the issue persists despite previous security modifications, suggesting a complex interaction between the patch application and the underlying memory management. Organizations utilizing pngcheck in security scanning, automated testing, or image processing workflows face significant risk, as this vulnerability can be exploited through image upload functionality in web applications, file sharing systems, or content management platforms. The impact is particularly severe in environments where automated image validation is performed without proper sandboxing or input sanitization, creating opportunities for attackers to deliver malicious png files that trigger the buffer overflow. The vulnerability also affects systems where pngcheck is used as part of security toolchains, potentially allowing adversaries to compromise the integrity of security scanning processes. Given the widespread use of pngcheck in various security and development environments, the potential for cascading effects exists, where exploitation of this vulnerability in one system could lead to broader security compromises across interconnected infrastructure components.
Mitigation strategies for CVE-2020-35511 must address both immediate remediation and long-term security hardening measures. The most direct solution involves upgrading to a patched version of pngcheck that properly implements bounds checking and memory validation for image data processing. System administrators should prioritize updating pngcheck installations across all environments where the utility is deployed, particularly in automated security scanning and testing workflows. Additionally, implementing input validation and sandboxing measures for image processing can significantly reduce the attack surface, as these controls prevent malformed image data from reaching the vulnerable parsing functions. Network segmentation and access controls should be enforced to limit the potential impact of exploitation, particularly in environments where pngcheck is used in automated processing pipelines. The implementation of proper memory protection mechanisms such as stack canaries, address space layout randomization, and data execution prevention can provide additional layers of defense against exploitation attempts. Organizations should also consider implementing file type validation and content inspection before processing images with pngcheck, ensuring that only properly formatted png files are processed by the utility. Regular security audits and vulnerability assessments should include checks for outdated pngcheck installations, particularly in automated environments where image validation is performed without user intervention. The vulnerability highlights the importance of comprehensive input validation and memory safety practices in security tools, as these utilities often process untrusted data from multiple sources and require robust protection against memory corruption vulnerabilities. Continuous monitoring and automated patch management processes should be established to ensure that security tools remain up-to-date with the latest vulnerability fixes and security enhancements.