CVE-2018-18584 in libmspack
Summary
by MITRE
In mspack/cab.h in libmspack before 0.8alpha and cabextract before 1.8, the CAB block input buffer is one byte too small for the maximal Quantum block, leading to an out-of-bounds write.
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Analysis
by VulDB Data Team • 05/30/2023
The vulnerability identified as CVE-2018-18584 represents a critical buffer management flaw within the mspack library and cabextract tools that are widely used for handling Microsoft Cabinet archive files. This issue affects versions prior to 0.8alpha for libmspack and 1.8 for cabextract, exposing systems that process CAB archives to potential exploitation through memory corruption attacks. The flaw manifests in the handling of CAB block input buffers where the allocated memory size falls short by exactly one byte when dealing with the maximum Quantum block size, creating a condition that allows attackers to write beyond the intended buffer boundaries.
The technical root cause of this vulnerability stems from improper buffer sizing calculations within the CAB file parsing logic. When the mspack library processes CAB archives, it allocates memory buffers based on calculated sizes for Quantum blocks, which are the fundamental units of data compression within CAB files. However, the implementation fails to account for the maximum possible Quantum block size, resulting in a buffer that is precisely one byte smaller than required. This seemingly minor discrepancy becomes catastrophic during actual processing when the decompression routines attempt to write data that exceeds the allocated buffer limits, causing memory corruption that can be leveraged for arbitrary code execution.
The operational impact of CVE-2018-18584 extends beyond simple memory corruption, as it creates multiple attack vectors for malicious actors seeking to compromise systems through CAB file manipulation. Attackers can craft specially crafted CAB archives that trigger the out-of-bounds write condition, potentially leading to privilege escalation, denial of service, or full system compromise depending on the execution environment. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and more specifically with CWE-787, which covers out-of-bounds write vulnerabilities. From an adversarial perspective, this flaw fits within the ATT&CK framework under the T1059.007 technique for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary code on vulnerable systems.
Mitigation strategies for CVE-2018-18584 require immediate patching of affected software versions to ensure proper buffer allocation for Quantum block processing. System administrators should prioritize updating libmspack to version 0.8alpha or later and cabextract to version 1.8 or higher, as these releases contain the necessary fixes for buffer size calculations. Additionally, organizations should implement defensive measures such as input validation for CAB file processing, sandboxing of archive extraction operations, and network monitoring to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of thorough buffer management in archive processing libraries, as even minor miscalculations in memory allocation can result in severe security implications that affect countless systems relying on standard archive handling functionality.