CVE-2016-8689 in libarchive
Summary
by MITRE
The read_Header function in archive_read_support_format_7zip.c in libarchive 3.2.1 allows remote attackers to cause a denial of service (out-of-bounds read) via multiple EmptyStream attributes in a header in a 7zip archive.
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Analysis
by VulDB Data Team • 08/15/2020
The vulnerability identified as CVE-2016-8689 resides within the libarchive library version 3.2.1, specifically in the archive_read_support_format_7zip.c component responsible for processing 7zip archive files. This flaw represents a critical security issue that enables remote attackers to execute a denial of service attack through carefully crafted malicious 7zip archives. The vulnerability manifests when the read_Header function encounters multiple EmptyStream attributes within a 7zip archive header structure, creating an exploitable condition that can be leveraged to disrupt normal system operations.
The technical implementation of this vulnerability stems from inadequate input validation within the archive parsing logic. When the read_Header function processes a 7zip archive containing multiple EmptyStream attributes, it fails to properly validate the boundaries of these attributes before attempting to access memory locations. This oversight results in an out-of-bounds read operation where the function attempts to access memory beyond the allocated buffer boundaries. The flaw aligns with CWE-125, which describes out-of-bounds read conditions that occur when software reads data beyond the intended buffer limits. The vulnerability represents a classic example of insufficient boundary checking in archive processing code, where the parser assumes valid input structure without proper validation of attribute counts and their associated memory access patterns.
From an operational perspective, this vulnerability poses significant risks to systems that process untrusted 7zip archives, particularly those deployed in email filtering systems, file upload validation services, or automated archive extraction environments. Attackers can craft malicious 7zip files containing multiple EmptyStream attributes that, when processed by vulnerable systems, trigger the out-of-bounds read condition. This condition typically results in application crashes, memory corruption, or system instability that manifests as denial of service conditions. The impact extends beyond simple service disruption as the vulnerability can potentially be chained with other exploits or used to bypass security controls in environments where archive processing is automated. According to ATT&CK framework concept T1203, this vulnerability enables an adversary to perform application or system exploitation through memory corruption techniques that can lead to service interruption and potential system compromise.
The mitigation strategies for CVE-2016-8689 primarily focus on immediate patching of the libarchive library to version 3.2.2 or later, which contains the necessary fixes for the boundary checking issues. Organizations should implement comprehensive input validation measures for all archive processing systems, including the deployment of sandboxed environments for archive extraction and content analysis. Network-based defenses can include implementing archive scanning and filtering rules that detect and quarantine suspicious archive files containing malformed EmptyStream attributes. Additionally, system administrators should consider implementing automated monitoring for application crashes or memory access violations that may indicate exploitation attempts. The vulnerability underscores the importance of proper memory management practices and input validation in archive processing libraries, with specific recommendations to implement robust boundary checks and defensive programming techniques that prevent out-of-bounds memory access conditions. Organizations should also conduct regular security assessments of their archive processing workflows to identify and remediate similar vulnerabilities in other third-party libraries and custom code implementations.