CVE-2015-8921 in libarchive
Summary
by MITRE
The ae_strtofflags function in archive_entry.c in libarchive before 3.2.0 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted mtree file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8921 resides within the libarchive library, specifically in the ae_strtofflags function located in archive_entry.c. This flaw represents a classic out-of-bounds read condition that can be exploited by remote attackers through the manipulation of mtree files. The libarchive library serves as a fundamental component for handling various archive formats including tar, zip, and mtree, making this vulnerability particularly concerning for systems that process untrusted archive data. The affected versions prior to 3.2.0 demonstrate a critical security gap where the function fails to properly validate input boundaries when processing mtree file entries, leading to memory access violations that can result in application crashes.
The technical implementation of this vulnerability stems from inadequate bounds checking within the ae_strtofflags function which processes flag strings in mtree format entries. When a maliciously crafted mtree file is processed, the function attempts to read memory locations beyond the allocated buffer boundaries, causing unpredictable behavior and system instability. This type of vulnerability falls under CWE-129, which specifically addresses insufficient validation of length of inputs, and represents a common pattern in archive processing libraries where string parsing functions fail to validate input parameters against expected ranges. The out-of-bounds read occurs during the parsing of file attributes and permissions specified in mtree entries, where the function assumes valid input structure without proper validation of string lengths or buffer limits.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially enable more sophisticated attacks depending on the system context and memory layout. Remote attackers can exploit this weakness by crafting malicious mtree files that trigger the vulnerable code path when processed by applications relying on libarchive. Systems that automatically process user-uploaded archives, archive servers, or any application that handles mtree format files are at risk. The vulnerability affects the broader ecosystem of applications including backup systems, file management utilities, and content delivery platforms that utilize libarchive for archive processing. This weakness can be leveraged in a variety of attack scenarios including service disruption, resource exhaustion, and potentially information disclosure depending on the memory access pattern and system configuration.
Mitigation strategies for CVE-2015-8921 primarily involve upgrading to libarchive version 3.2.0 or later, where the bounds checking has been properly implemented to prevent out-of-bounds memory access. System administrators should conduct comprehensive vulnerability assessments to identify all applications and services that rely on libarchive and ensure they are updated to patched versions. Network segmentation and input validation controls can provide additional defense-in-depth measures, though the primary remediation remains the library upgrade. The vulnerability demonstrates the importance of proper input validation and bounds checking in security-critical components, aligning with ATT&CK technique T1059.007 for execution through archive files and T1499.004 for endpoint denial of service. Organizations should implement continuous monitoring for similar patterns in other archive processing libraries and maintain updated threat intelligence to identify potential variants of this class of vulnerability that may exist in related software components.