CVE-2015-8929 in libarchive
Summary
by MITRE
Memory leak in the __archive_read_get_extract function in archive_read_extract2.c in libarchive before 3.2.0 allows remote attackers to cause a denial of service via a tar file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8929 represents a critical memory management flaw within the libarchive library version 3.1.2 and earlier, specifically within the __archive_read_get_extract function located in archive_read_extract2.c. This memory leak occurs during the extraction process of tar files, where the library fails to properly release allocated memory resources when processing malformed or specially crafted archive files. The issue stems from inadequate memory cleanup mechanisms that persistently allocate memory without subsequent deallocation, creating a condition where repeated processing of archive files can lead to progressive memory consumption. This flaw affects systems that rely on libarchive for handling archive operations, particularly those processing untrusted tar files from external sources.
The technical implementation of this vulnerability demonstrates a classic memory leak pattern where the __archive_read_get_extract function does not properly handle memory allocation for archive extraction contexts. When processing tar files, the function allocates memory structures to hold file metadata and content information but fails to ensure proper deallocation when the extraction process completes or encounters errors. This behavior creates a cumulative memory consumption issue that can be exploited by remote attackers who craft malicious tar files designed to trigger the leak condition repeatedly. The vulnerability is particularly dangerous because it operates at the archive processing layer, where it can be triggered by any application using libarchive for file extraction operations, including web applications, backup systems, and file processing utilities.
The operational impact of CVE-2015-8929 extends beyond simple resource exhaustion to potentially compromise system availability and stability. Remote attackers can exploit this vulnerability by delivering specially crafted tar files that, when processed by affected systems, cause progressive memory consumption until system resources are exhausted. This denial of service condition can affect any service or application that utilizes libarchive for archive processing, including web servers handling file uploads, backup and recovery systems, and content delivery platforms. The vulnerability is particularly concerning in server environments where multiple archive files are processed continuously, as the memory leak can accumulate over time and eventually cause system crashes or complete service unavailability. Additionally, the vulnerability affects both local and remote exploitation scenarios, making it applicable to a wide range of attack vectors including web-based file upload interfaces and automated archive processing workflows.
Mitigation strategies for CVE-2015-8929 primarily focus on upgrading to libarchive version 3.2.0 or later, where the memory leak has been addressed through proper memory management practices. System administrators should prioritize patching affected systems and applications that depend on libarchive, particularly those handling untrusted archive files from external sources. Additional protective measures include implementing input validation and sanitization for archive file processing, limiting the number of archive files processed in a single session, and monitoring system memory usage for unusual consumption patterns. Security teams should also consider implementing network-level controls to restrict access to archive processing services and deploy intrusion detection systems capable of identifying potential exploitation attempts. The vulnerability aligns with CWE-401, which categorizes memory leaks as a fundamental weakness in memory management, and represents a typical example of how improper resource handling can lead to denial of service conditions. Organizations should also consider implementing application-level sandboxing for archive processing operations to limit the impact of potential exploitation and ensure that memory leaks do not affect overall system stability.