CVE-2016-4804 in dosfstools
Summary
by MITRE
The read_boot function in boot.c in dosfstools before 4.0 allows attackers to cause a denial of service (crash) via a crafted filesystem, which triggers a heap-based buffer overflow in the (1) read_fat function or an out-of-bounds heap read in (2) get_fat function.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-4804 affects dosfstools version 3.0.27 and earlier, representing a critical security flaw in the handling of FAT filesystems. This issue resides within the boot.c file, specifically in the read_boot function that processes filesystem boot sectors. The vulnerability stems from inadequate input validation and memory management when parsing maliciously crafted filesystem structures, creating a dangerous condition that can be exploited by attackers to cause system instability. The flaw demonstrates characteristics consistent with heap-based buffer overflow conditions and out-of-bounds memory access patterns, making it particularly dangerous in environments where filesystem parsing is automated or untrusted data is processed.
The technical implementation of this vulnerability involves multiple attack vectors that exploit different memory access patterns within the dosfstools library. When the read_boot function processes a malformed filesystem, it fails to properly validate the size and structure of the boot sector data before attempting to read FAT table entries. This leads to a heap-based buffer overflow in the read_fat function, where insufficient bounds checking allows data to be written beyond allocated memory boundaries. Additionally, the get_fat function experiences an out-of-bounds heap read condition, where the code attempts to access memory locations that extend beyond the allocated buffer space. These memory corruption issues are classified under CWE-121, heap-based buffer overflow, and CWE-125, out-of-bounds read, respectively, both of which are fundamental memory safety issues that have been extensively documented in cybersecurity literature and are commonly exploited in privilege escalation attacks.
The operational impact of CVE-2016-4804 extends beyond simple denial of service, as it creates potential pathways for more sophisticated attacks within computing environments. Systems utilizing dosfstools for filesystem operations, including embedded devices, mobile platforms, and Linux systems that mount FAT filesystems, become vulnerable to crashes that can be triggered by simply mounting a maliciously crafted filesystem image. This vulnerability can be particularly dangerous in automated environments where filesystem mounting occurs without user intervention, such as in mobile devices, embedded systems, or server environments that process untrusted storage media. The attack surface is broadened by the fact that this vulnerability can be exploited through various attack vectors including removable storage devices, network file sharing protocols, and automated mounting processes that do not validate filesystem integrity before processing. According to ATT&CK framework category T1499, this vulnerability could be leveraged for system resource exploitation and denial of service attacks, potentially disrupting critical system operations and creating opportunities for further exploitation.
Mitigation strategies for CVE-2016-4804 require immediate implementation of version updates to dosfstools 4.0 or later, which includes comprehensive fixes for the identified buffer overflow and out-of-bounds read conditions. System administrators should prioritize patching all affected systems and implementing automated monitoring for filesystem mounting operations to detect potential exploitation attempts. The vulnerability's classification as a heap-based buffer overflow and out-of-bounds memory access aligns with security best practices for input validation and memory management, emphasizing the need for defensive programming techniques such as bounds checking, stack canaries, and address space layout randomization. Organizations should also implement network segmentation and access controls to limit the potential impact of exploitation, while maintaining regular vulnerability assessments to identify similar memory safety issues in other software components. The remediation process should include comprehensive testing of patched systems to ensure that filesystem operations function correctly without introducing new stability issues, particularly in embedded environments where resource constraints may exacerbate the effects of memory corruption vulnerabilities.