CVE-2015-4471 in libmspack
Summary
by MITRE
Off-by-one error in the lzxd_decompress function in lzxd.c in libmspack before 0.5 allows remote attackers to cause a denial of service (buffer under-read and application crash) via a crafted CAB archive.
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Analysis
by VulDB Data Team • 05/21/2022
The vulnerability identified as CVE-2015-4471 represents a critical off-by-one error within the lzxd_decompress function of the libmspack library version 0.5 and earlier. This flaw exists in the lzxd.c source file and specifically affects the decompression functionality used to process CAB archives. The issue arises from improper boundary checking during the decompression process, creating a scenario where the application reads memory locations before the intended buffer boundaries. Such buffer under-read conditions are particularly dangerous as they can lead to unpredictable behavior and system instability. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, which directly relates to the flawed boundary checking mechanism that fails to properly validate input parameters before array access operations. This type of vulnerability falls within the ATT&CK framework under the technique T1499.004 for Network Denial of Service, as it can be exploited to cause application crashes and system unavailability.
The technical exploitation of this vulnerability requires a remote attacker to craft a specially malformed CAB archive that triggers the flawed decompression logic in libmspack. When the affected library processes this malicious archive, the off-by-one error causes the lzxd_decompress function to attempt reading from memory locations that precede the actual data buffer. This under-read condition can result in accessing uninitialized memory, causing the application to crash or behave unpredictably. The impact extends beyond simple application termination as the under-read can potentially expose sensitive information from adjacent memory regions or trigger more severe memory corruption issues. The vulnerability affects any system or application that relies on libmspack for CAB archive decompression, including web servers, file processing systems, and archive management tools that handle user-uploaded content.
The operational impact of CVE-2015-4471 manifests as a reliable denial of service condition that can be triggered remotely without requiring authentication or specialized privileges. Attackers can simply upload or provide a malicious CAB file to any system utilizing the vulnerable libmspack library, resulting in immediate service disruption. This vulnerability is particularly concerning in environments where automated processing of user-uploaded archives occurs, as it can lead to cascading failures and system-wide availability issues. The vulnerability's severity is amplified by its ease of exploitation and the fact that it can affect multiple applications and systems simultaneously. Organizations relying on legacy systems or applications that have not been updated to libmspack version 0.5 or later remain vulnerable to this attack vector.
Mitigation strategies for CVE-2015-4471 primarily involve immediate patching of the libmspack library to version 0.5 or later, which contains the necessary fixes for the off-by-one error. System administrators should conduct thorough vulnerability assessments to identify all systems utilizing affected versions of libmspack and ensure timely updates are deployed across the infrastructure. Additional protective measures include implementing input validation and sanitization for all archive processing functions, deploying network intrusion detection systems to monitor for suspicious archive file uploads, and establishing robust application sandboxing mechanisms to limit the impact of potential exploitation. Organizations should also consider implementing automated patch management processes and regular security audits to prevent similar vulnerabilities from remaining unaddressed in their software supply chains. The fix implemented in libmspack 0.5 addresses the root cause by properly validating array indices and ensuring that buffer access operations remain within defined boundaries, thereby preventing the under-read conditions that led to the vulnerability.