CVE-2015-8916 in libarchive
Summary
by MITRE
bsdtar in libarchive before 3.2.0 returns a success code without filling the entry when the header is a "split file in multivolume RAR," which allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a crafted rar file.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8916 affects bsdtar, a command-line utility included in the libarchive library, specifically versions prior to 3.2.0. This flaw resides in the handling of multivolume RAR archives where the archive is split across multiple files, creating a complex scenario for archive extraction processes. The issue manifests when bsdtar encounters a "split file in multivolume RAR" header structure, which represents a legitimate archive format used by the RAR archiving tool. The vulnerability is classified under CWE-476 as NULL pointer dereference, indicating a fundamental flaw in pointer validation during archive processing operations.
The technical implementation of this vulnerability occurs during the parsing of archive headers where bsdtar fails to properly validate the integrity of multivolume RAR structures. When processing a crafted RAR file that contains split volume headers, the software returns a success code indicating normal operation while simultaneously failing to properly initialize or populate the entry structure. This inconsistent behavior creates a scenario where downstream code attempts to access memory locations that were never properly allocated or initialized. The NULL pointer dereference occurs because the entry structure remains in an uninitialized state despite the function returning a successful status code, leading to a crash when the program attempts to access the uninitialized pointer.
From an operational perspective, this vulnerability presents a significant denial of service risk for systems utilizing bsdtar for archive processing. Remote attackers can exploit this weakness by crafting malicious RAR files that contain split volume headers, causing the target system to crash whenever the archive is processed. The impact extends beyond simple service disruption as the vulnerability can affect any application or system that relies on libarchive for archive handling, including backup systems, file servers, and content delivery platforms. The vulnerability is particularly concerning in automated environments where archive processing occurs without user intervention, as it can lead to unattended system crashes and potential availability disruptions.
The exploitation of CVE-2015-8916 aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through exploitation of software vulnerabilities. This vulnerability represents a classic case of improper error handling and input validation where the software assumes successful processing without verifying that all necessary data structures have been properly initialized. The flaw demonstrates poor defensive programming practices that violate fundamental security principles, as the system should not return success codes for operations that have not been completed correctly. Organizations should implement immediate mitigation through patching libarchive to version 3.2.0 or later, while also considering input validation measures for archive processing to prevent exploitation of similar vulnerabilities in other components of the system infrastructure.