CVE-2015-8920 in libarchive
Summary
by MITRE
The _ar_read_header function in archive_read_support_format_ar.c in libarchive before 3.2.0 allows remote attackers to cause a denial of service (out-of-bounds stack read) via a crafted ar file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8920 represents a critical security flaw within the libarchive library, specifically in the archive_read_support_format_ar.c component. This issue affects versions prior to 3.2.0 and manifests as an out-of-bounds stack read condition that can be exploited by remote attackers through carefully crafted ar archive files. The libarchive library serves as a fundamental component for handling various archive formats including ar, tar, zip, and others, making this vulnerability particularly concerning given its widespread use across numerous applications and operating systems. The flaw occurs within the _ar_read_header function which processes the header section of ar archives, a format commonly used for creating and managing static libraries in unix-like systems and software development environments.
The technical nature of this vulnerability stems from inadequate input validation and boundary checking within the archive reading process. When the _ar_read_header function processes a malformed ar file, it fails to properly validate the size and structure of the archive header before attempting to read data from the stack memory. This allows an attacker to craft a malicious ar file that contains malformed header information, causing the function to read beyond the allocated stack buffer boundaries. The out-of-bounds read occurs because the code does not verify that the header data conforms to expected size constraints or format specifications before performing memory operations. This type of vulnerability falls under CWE-129, which specifically addresses insufficient validation of length of inputs, and represents a classic example of a buffer overflow condition that can lead to denial of service or potentially more severe exploitation depending on the execution environment.
The operational impact of CVE-2015-8920 extends beyond simple denial of service scenarios, as it can affect any system or application that relies on libarchive for processing ar archives. This includes software development tools like compilers and build systems, system administration utilities, backup and recovery applications, and various network services that handle file uploads or archive processing. The vulnerability is particularly dangerous because it can be triggered remotely through network-based file transfers or web applications that accept archive uploads, allowing attackers to disrupt services without requiring local system access. In environments where automated processing of user-uploaded archives occurs, such as web applications, content management systems, or build servers, this vulnerability can lead to complete service disruption and potential system instability. The attack vector is especially concerning given that ar archives are commonly used in software development workflows, making this vulnerability exploitable in numerous legitimate software distribution and compilation scenarios.
Mitigation strategies for CVE-2015-8920 primarily involve upgrading to libarchive version 3.2.0 or later, where the vulnerability has been addressed through improved input validation and boundary checking mechanisms. System administrators should prioritize patching affected systems and applications that depend on libarchive, particularly those handling untrusted archive files from external sources. Additional defensive measures include implementing strict file type validation and sanitization for archive uploads, deploying network-based intrusion detection systems to monitor for suspicious archive file patterns, and configuring applications to limit the size and complexity of processed archives. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation or denial of service, and demonstrates the importance of maintaining up-to-date third-party libraries in software supply chains. Organizations should also consider implementing automated vulnerability scanning and patch management processes to identify and remediate similar issues across their software ecosystems, as this vulnerability could potentially be leveraged in broader attack chains targeting system stability and availability.