CVE-2016-3977 in giflib
Summary
by MITRE
Heap-based buffer overflow in util/gif2rgb.c in gif2rgb in giflib 5.1.2 allows remote attackers to cause a denial of service (application crash) via the background color index in a GIF file.
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Analysis
by VulDB Data Team • 10/06/2024
The vulnerability identified as CVE-2016-3977 represents a critical heap-based buffer overflow flaw within the giflib library version 5.1.2, specifically affecting the gif2rgb utility component. This issue manifests in the util/gif2rgb.c file where improper input validation occurs during the processing of GIF file background color index values. The flaw arises when the application attempts to handle malformed GIF files containing oversized or invalid background color index values, leading to memory corruption in the heap allocation regions. Such buffer overflows typically occur when programs write data beyond the allocated memory boundaries, potentially causing unpredictable behavior including application crashes or system instability. The vulnerability is particularly concerning as it can be exploited remotely through crafted GIF files, making it a significant threat to applications that process user-supplied graphics content.
The technical exploitation of this vulnerability involves the manipulation of GIF file structures, specifically targeting the background color index field within the GIF image header. When gif2rgb processes a malicious GIF file, it fails to properly validate the background color index value against the actual color table size, allowing an attacker to write beyond the allocated buffer space. This type of heap corruption can result in memory corruption that manifests as application crashes, segmentation faults, or potentially more severe consequences if the attacker can influence the memory layout. The vulnerability falls under the CWE-121 heap-based buffer overflow category, which is classified as a common weakness in software security practices. The flaw demonstrates poor input validation and memory management practices that are fundamental to secure coding standards.
The operational impact of CVE-2016-3977 extends beyond simple denial of service conditions, as it can affect a wide range of applications that utilize the giflib library for GIF image processing. Systems that automatically process user-uploaded GIF files, web applications serving dynamic graphics, or content management systems handling image uploads become vulnerable to this attack vector. The remote exploitation capability means that attackers can trigger the vulnerability without requiring local access, making it particularly dangerous in web-facing applications. From an attack framework perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the 'Execution' and 'Resource Exhaustion' tactics, where adversaries can cause system instability through memory corruption. The vulnerability can be exploited in various contexts including web applications, file processing systems, and content filtering solutions that rely on giflib for image handling.
Mitigation strategies for CVE-2016-3977 should focus on immediate library updates and input validation improvements. The most effective solution involves upgrading to giflib version 5.1.3 or later, where the buffer overflow has been addressed through proper bounds checking and input validation. Organizations should implement comprehensive input sanitization measures, including strict validation of GIF file structures and color table sizes before processing. Additionally, deployment of web application firewalls and content filtering systems can help detect and block malicious GIF files before they reach vulnerable applications. Security teams should also consider implementing memory protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checks to reduce the impact of potential exploitation attempts. The vulnerability highlights the importance of regular security updates and proper code review processes, particularly for libraries handling user-supplied binary data. System administrators should conduct thorough vulnerability assessments to identify all systems using affected versions of giflib and implement remediation measures promptly to prevent potential exploitation by threat actors.