CVE-2015-8836 in FuseISO
Summary
by MITRE
Integer overflow in the isofs_real_read_zf function in isofs.c in FuseISO 20070708 might allow remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a large ZF block size in an ISO file, leading to a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 02/03/2019
The vulnerability identified as CVE-2015-8836 represents a critical integer overflow flaw within the FuseISO library version 20070708, specifically within the isofs_real_read_zf function located in the isofs.c source file. This issue manifests when processing ISO filesystem images that contain a large ZF block size, creating a dangerous condition that can be exploited by remote attackers to compromise system stability and potentially execute arbitrary code. The vulnerability operates at the intersection of file system parsing and memory management, where improper handling of integer values leads to memory corruption. The affected software component serves as a filesystem driver that enables mounting of ISO images, making it a potential attack vector for systems that rely on this functionality for file access operations. This flaw falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a common weakness in software design that directly impacts memory safety and application stability. The vulnerability is particularly concerning because it can be triggered through standard file access operations, requiring no special privileges beyond the ability to access or process ISO files.
The technical mechanism of this vulnerability involves the improper validation of block size parameters within the ZF (Zero Fill) block processing logic. When an ISO file contains a ZF block with an excessively large size parameter, the integer overflow occurs during the calculation of buffer allocation requirements. This overflow results in a heap-based buffer overflow condition where the application attempts to write beyond allocated memory boundaries. The memory corruption manifests as an application crash or segmentation fault, leading to denial of service conditions that can be exploited remotely by attackers who can control the input ISO file. The vulnerability is particularly dangerous because it can be triggered through legitimate file processing operations, making it difficult to distinguish between malicious and benign input. The flaw demonstrates a classic memory safety issue where unsigned integer arithmetic operations fail to properly validate input parameters, leading to unpredictable memory access patterns and potential code execution.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the environment where the vulnerable software is deployed. Systems that process untrusted ISO files, such as web applications, file sharing platforms, or automated processing systems, become vulnerable to remote exploitation. The vulnerability can be leveraged to cause service disruption, data loss, or potentially provide a foothold for further attacks within the compromised system. Attackers can craft specially formatted ISO files that trigger the integer overflow condition, making this a particularly dangerous issue for systems that automatically process or validate ISO content. The vulnerability affects any system using FuseISO 20070708 or earlier versions, including Linux systems that utilize this library for ISO file mounting and processing. Organizations relying on this library for file system operations, particularly in environments where ISO files are regularly processed, face significant risk exposure. The vulnerability is also relevant to the ATT&CK framework under the T1059.007 technique for command and control through file and directory permissions, as it can be used to create persistent access points through compromised file processing systems.
Mitigation strategies for this vulnerability require immediate software updates and patches to address the integer overflow condition in the affected FuseISO library. System administrators should prioritize updating to patched versions of FuseISO that properly validate ZF block size parameters and implement robust input sanitization measures. The implementation of proper integer overflow checks and buffer size validation should be enforced throughout the application's file processing pipeline to prevent similar issues. Organizations should also consider implementing network segmentation and access controls to limit exposure to potentially malicious ISO file content, particularly in environments where untrusted users can upload or process files. Additionally, regular security assessments of file processing systems and input validation mechanisms should be conducted to identify and remediate similar vulnerabilities. The vulnerability highlights the importance of secure coding practices and the need for comprehensive testing of integer arithmetic operations in memory-sensitive applications. System monitoring and intrusion detection should be enhanced to identify suspicious file processing activities that may indicate exploitation attempts. Organizations should also consider implementing sandboxing techniques for ISO file processing to isolate potential memory corruption issues and prevent escalation to system-wide compromise.