CVE-2016-8688 in libarchive
Summary
by MITRE
The mtree bidder in libarchive 3.2.1 does not keep track of line sizes when extending the read-ahead, which allows remote attackers to cause a denial of service (crash) via a crafted file, which triggers an invalid read in the (1) detect_form or (2) bid_entry function in libarchive/archive_read_support_format_mtree.c.
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Analysis
by VulDB Data Team • 08/15/2020
The vulnerability identified as CVE-2016-8688 affects the mtree bidder functionality within libarchive version 3.2.1, representing a critical denial of service flaw that can be exploited remotely through specially crafted archive files. This issue resides in the archive_read_support_format_mtree.c source file where the mtree format reader fails to properly manage line size tracking during read-ahead operations. The flaw manifests when the system attempts to process malformed mtree files that trigger invalid memory reads in either the detect_form or bid_entry functions, ultimately leading to application crashes and service disruption.
The technical root cause of this vulnerability stems from inadequate input validation and memory management within the mtree format parser. When processing archive files, the mtree bidder component employs a read-ahead mechanism to optimize parsing performance by pre-reading portions of the file. However, the implementation fails to maintain proper tracking of line boundaries and buffer sizes when extending these read-ahead buffers. This oversight creates a scenario where maliciously constructed input can cause the parser to attempt reading beyond allocated memory boundaries, resulting in invalid memory access patterns that terminate the application process.
From an operational perspective, this vulnerability presents significant risks to systems that utilize libarchive for processing untrusted archive files, particularly in environments where automated archive extraction occurs. Attackers can craft mtree files containing carefully constructed line length variations that cause the read-ahead buffer to overflow or underflow, leading to segmentation faults and application crashes. The impact extends beyond simple service disruption as this vulnerability can be leveraged in broader attack chains where denial of service conditions are used to facilitate more sophisticated exploitation techniques.
The vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and demonstrates characteristics consistent with buffer overflow conditions in parsing components. From an attack framework perspective, this issue maps to ATT&CK technique T1499.004 for network denial of service, where adversaries leverage software flaws to disrupt services. The flaw also relates to ATT&CK technique T1059.007 for command and scripting interpreter, as the crash conditions can be triggered through automated parsing of archive content in various system contexts.
Mitigation strategies should focus on immediate patching of libarchive to versions that address the buffer management issues in the mtree bidder component. Organizations should implement strict input validation for all archive file processing, particularly for mtree format files from untrusted sources. Network segmentation and access controls should be enforced to limit exposure of systems that process archive files. Additionally, implementing proper error handling and graceful degradation mechanisms can help prevent complete service disruption when such vulnerabilities are encountered. Regular security assessments and vulnerability scanning should include checks for outdated libarchive versions to prevent exploitation of this and similar parsing vulnerabilities.