CVE-2015-8926 in libarchive
Summary
by MITRE
The archive_read_format_rar_read_data function in archive_read_support_format_rar.c in libarchive before 3.2.0 allows remote attackers to cause a denial of service (crash) via a crafted rar archive.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8926 represents a critical denial of service flaw within the libarchive library, specifically affecting versions prior to 3.2.0. This issue resides in the archive_read_format_rar_read_data function located within the archive_read_support_format_rar.c source file, which handles decompression and processing of.rar archive files. The flaw manifests when the library processes malformed or specially crafted.rar archives, leading to a crash condition that can be exploited remotely by attackers. The vulnerability impacts systems that utilize libarchive for handling compressed file formats, particularly those that accept user-provided archives without proper validation. This type of vulnerability falls under the category of memory corruption issues and is classified as a buffer overflow or heap-based vulnerability that can result in application termination.
The technical mechanism behind this vulnerability involves improper input validation within the RAR format parser implementation. When the archive_read_format_rar_read_data function encounters a malformed RAR archive structure, it fails to properly handle edge cases or invalid data sequences during the decompression process. This lack of proper bounds checking and error handling causes the application to access memory locations outside of allocated buffers or attempt operations on corrupted data structures. The flaw essentially creates a path where untrusted input can trigger undefined behavior in the memory management subsystem of libarchive, leading to segmentation faults or other critical runtime errors that result in application crashes. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of how improper input validation can lead to denial of service attacks.
The operational impact of CVE-2015-8926 extends beyond simple service disruption, as it can be leveraged by remote attackers to systematically crash applications that depend on libarchive for archive processing. Systems commonly affected include web servers, file sharing platforms, email servers, and content management systems that handle user-uploaded files. The vulnerability can be particularly dangerous in automated environments where continuous service availability is critical, as attackers can repeatedly exploit the flaw to maintain persistent denial of service conditions. This vulnerability can also be chained with other exploits in advanced attack scenarios, potentially leading to more severe consequences depending on the target application's architecture and the privileges under which it operates. From an operational security perspective, this vulnerability demonstrates the importance of input validation and proper error handling in security-critical libraries that process untrusted data, as highlighted in the ATT&CK framework under the technique of "Exploitation for Defense Evasion" where attackers leverage system weaknesses to disrupt services.
Mitigation strategies for CVE-2015-8926 primarily focus on upgrading to libarchive version 3.2.0 or later, where the vulnerability has been addressed through improved input validation and error handling mechanisms. Organizations should conduct comprehensive vulnerability assessments to identify all systems that utilize affected versions of libarchive and implement patch management procedures to ensure timely updates. Additionally, implementing proper input sanitization at application layers that utilize libarchive can provide defense-in-depth protection, though this approach is less reliable than patching the underlying library. Network-level protections such as content filtering and sandboxing mechanisms can also help mitigate the risk of exploitation by preventing malformed archives from reaching vulnerable applications. Security monitoring should include detection of unusual crash patterns or service disruptions that may indicate exploitation attempts, and organizations should maintain updated threat intelligence feeds to track related attack patterns and emerging variants of this vulnerability.