CVE-2018-11438 in Libmobi
Summary
by MITRE
The mobi_decompress_lz77 function in compression.c in Libmobi 0.3 allows remote attackers to cause remote code execution (heap-based buffer overflow) via a crafted mobi file.
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Analysis
by VulDB Data Team • 03/17/2023
The vulnerability identified as CVE-2018-11438 resides within the Libmobi 0.3 library's mobi_decompress_lz77 function located in compression.c. This flaw represents a critical heap-based buffer overflow that can be exploited by remote attackers through the careful crafting of malicious mobi files. The vulnerability stems from inadequate input validation and bounds checking within the decompression routine that processes lz77 compressed data streams. When a maliciously constructed mobi file is processed by the vulnerable library, the decompression function fails to properly validate the size of data being read into allocated heap buffers, leading to memory corruption that can be leveraged for arbitrary code execution.
The technical nature of this vulnerability aligns with CWE-121, heap-based buffer overflow, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under T1059.007 for execution through command and scripting interpreter. The flaw occurs during the decompression process where the mobi_decompress_lz77 function does not properly verify the length of compressed data against the allocated buffer space, allowing attackers to write beyond the bounds of heap-allocated memory regions. This memory corruption can overwrite adjacent memory structures including return addresses, function pointers, or other critical data, enabling attackers to redirect program execution flow and potentially execute malicious code with the privileges of the affected application.
The operational impact of CVE-2018-11438 extends beyond simple remote code execution to encompass significant security risks for applications and systems that utilize the Libmobi library for processing mobi formatted documents. This includes e-book readers, document processing applications, and content management systems that handle mobi files from untrusted sources. The vulnerability can be exploited in various attack scenarios including web-based delivery, email attachments, or file sharing platforms where mobi files are commonly encountered. The remote exploitation capability means that attackers do not need physical access to the target system, making this vulnerability particularly dangerous for widely deployed applications and services that process user-uploaded content. Security professionals must consider this vulnerability when assessing risk in systems that process mobi documents, as successful exploitation could lead to complete system compromise.
Mitigation strategies for CVE-2018-11438 should focus on immediate library updates and implementation of robust input validation measures. The primary remediation involves upgrading to a patched version of Libmobi that addresses the buffer overflow in the compression.c file. Organizations should also implement defensive programming practices including bounds checking, memory allocation validation, and input sanitization before processing any mobi files. Additionally, network segmentation and access controls can help limit the potential impact of exploitation attempts. Security monitoring should be enhanced to detect unusual file processing patterns or memory allocation behaviors that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of thorough input validation in decompression and parsing functions, particularly in libraries that process untrusted binary formats and highlights the necessity of adhering to secure coding practices as outlined in industry standards such as the OWASP Secure Coding Practices and the CERT Secure Coding Standards.