CVE-2021-3496 in jhead
Summary
by MITRE • 04/23/2021
A heap-based buffer overflow was found in jhead in version 3.06 in Get16u() in exif.c when processing a crafted file.
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Analysis
by VulDB Data Team • 04/29/2021
The heap-based buffer overflow vulnerability identified as CVE-2021-3496 resides within the jhead utility version 3.06, specifically within the Get16u() function located in the exif.c source file. This flaw represents a critical security weakness that can be exploited through the careful crafting of image files containing malformed EXIF metadata. The vulnerability manifests when the application processes these maliciously constructed files, leading to unpredictable behavior and potential system compromise. The issue stems from inadequate input validation and memory management practices within the EXIF parsing logic, creating an opportunity for attackers to manipulate heap memory through crafted data structures.
The technical execution of this vulnerability occurs during the parsing of EXIF metadata within JPEG image files, where the Get16u() function attempts to read 16-bit unsigned integers from the file buffer without proper bounds checking. When confronted with malformed data that exceeds expected buffer boundaries, the function fails to validate input lengths, resulting in memory corruption that can overwrite adjacent heap allocations. This heap-based overflow creates conditions where attacker-controlled data can overwrite critical memory regions, potentially leading to arbitrary code execution or denial of service conditions. The vulnerability is classified as a CWE-121 heap-based buffer overflow, which is a well-documented class of memory safety issues that has been extensively studied in cybersecurity research and has direct implications for application security.
The operational impact of CVE-2021-3496 extends beyond simple denial of service scenarios, as it represents a significant threat to systems that process untrusted image files. Applications utilizing jhead for image metadata extraction, including web applications, content management systems, and digital asset management platforms, become vulnerable to remote code execution attacks. Attackers can leverage this vulnerability by uploading or processing specially crafted JPEG files that trigger the buffer overflow during EXIF parsing operations. The attack surface is particularly concerning in environments where users can upload images, as this creates an automated path for exploitation. This vulnerability aligns with ATT&CK technique T1203, which describes the use of file execution through manipulation of image processing utilities, and represents a common vector for privilege escalation attacks in web applications.
Mitigation strategies for CVE-2021-3496 should prioritize immediate patching of affected jhead versions to address the underlying buffer overflow in the Get16u() function. System administrators should implement input validation measures that sanitize EXIF metadata before processing, including length checks and bounds verification for all parsed integer values. Network segmentation and application whitelisting can help reduce the attack surface by limiting access to vulnerable image processing functions. Additionally, implementing proper memory protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checks can provide additional defense-in-depth layers. The vulnerability demonstrates the importance of following secure coding practices and adheres to CWE guidelines for preventing buffer overflow conditions through proper input validation and memory management. Organizations should also consider deploying intrusion detection systems that can identify suspicious image file processing patterns and maintain comprehensive monitoring of systems that utilize jhead or similar image processing utilities for security incident response.