CVE-2015-8934 in libarchive
Summary
by MITRE
The copy_from_lzss_window function in archive_read_support_format_rar.c in libarchive 3.2.0 and earlier allows remote attackers to cause a denial of service (out-of-bounds heap read) via a crafted rar file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8934 represents a critical heap-based out-of-bounds read flaw within the libarchive library version 3.2.0 and earlier. This issue resides in the copy_from_lzss_window function located in the archive_read_support_format_rar.c file, which processes.rar archive files. The flaw manifests when the library attempts to decompress RAR format archives, specifically during the handling of LZSS (Lempel-Ziv-Storer-Szymanski) compressed data streams. The vulnerability arises from insufficient bounds checking during the decompression process, allowing maliciously crafted RAR files to trigger memory access violations that result in denial of service conditions.
The technical implementation of this vulnerability stems from improper validation of compressed data within the RAR decompression algorithm. When processing a specially crafted RAR file, the copy_from_lzss_window function fails to properly verify array indices or buffer boundaries before accessing heap memory locations. This insufficient input validation creates a scenario where an attacker can manipulate the compressed data stream to reference memory addresses outside the intended buffer boundaries, leading to out-of-bounds heap reads. The flaw specifically affects the decompression logic that handles the LZSS window management, where the algorithm maintains a sliding window of previously decompressed data to enable efficient compression. When the compressed data contains invalid or maliciously constructed references to this window, the function attempts to read from memory locations that may not be properly allocated or accessible.
The operational impact of CVE-2015-8934 extends beyond simple denial of service, as it represents a fundamental security weakness that can be exploited by remote attackers to disrupt services. Systems that utilize libarchive for processing user-uploaded or externally sourced RAR files become vulnerable to this attack vector, potentially affecting web applications, file processing services, and content management systems. The vulnerability can be triggered through any application that relies on libarchive for RAR archive handling, including but not limited to email servers, file sharing platforms, and automated content processing pipelines. The out-of-bounds read condition typically results in application crashes or hangs, effectively rendering the targeted service unavailable to legitimate users while providing no direct mechanism for arbitrary code execution or privilege escalation.
Security mitigation strategies for CVE-2015-8934 primarily focus on immediate remediation through library updates and comprehensive input validation. The most effective solution involves upgrading to libarchive version 3.2.1 or later, where the vulnerability has been addressed through proper bounds checking implementations in the affected function. Organizations should also implement defensive programming practices such as input sanitization, where RAR files are validated before processing, and robust error handling that can gracefully manage malformed archive data. Network-level protections can include implementing file type filtering and content scanning mechanisms to prevent potentially malicious RAR files from reaching systems that process archives. Additionally, security monitoring should be enhanced to detect unusual application behavior patterns that may indicate exploitation attempts, and system administrators should conduct regular vulnerability assessments to identify and remediate similar issues across their software infrastructure. This vulnerability aligns with CWE-125 out-of-bounds read and represents a typical example of how improper input validation can lead to denial of service conditions, potentially mapping to ATT&CK technique T1499.004 for network denial of service attacks through malformed data processing.