CVE-2016-4809 in libarchive
Summary
by MITRE
The archive_read_format_cpio_read_header function in archive_read_support_format_cpio.c in libarchive before 3.2.1 allows remote attackers to cause a denial of service (application crash) via a CPIO archive with a large symlink.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2016-4809 represents a critical denial of service flaw within the libarchive library, specifically affecting the archive_read_format_cpio_read_header function in the archive_read_support_format_cpio.c module. This issue exists in libarchive versions prior to 3.2.1 and enables remote attackers to trigger application crashes through carefully crafted CPIO archives containing oversized symbolic links. The flaw manifests when the library attempts to process malformed CPIO archive entries that contain symlink entries exceeding normal size constraints, leading to unpredictable application behavior and potential system instability.
The technical implementation of this vulnerability stems from inadequate input validation within the CPIO format parser. When the archive_read_format_cpio_read_header function encounters a symlink entry with an excessively large size field, the library fails to properly handle the boundary conditions, resulting in memory corruption or stack overflow conditions. This particular flaw aligns with CWE-129, which addresses improper validation of length values, and represents a classic example of insufficient bounds checking in archive processing libraries. The vulnerability operates at the parsing layer of the archive handling system, where the library's internal buffer management and size validation mechanisms prove inadequate when confronted with malformed symlink data structures.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited in various real-world scenarios involving archive processing applications. Systems that rely on libarchive for handling user-uploaded content, automated backup operations, or network-based archive extraction become particularly vulnerable when processing untrusted CPIO archives. Attackers can leverage this weakness to perform targeted denial of service attacks against services that utilize libarchive functionality, potentially affecting web applications, file servers, backup systems, and any software that processes CPIO formatted archives. The attack vector is particularly concerning because it requires no special privileges or authentication, making it accessible to remote unauthenticated users who can simply provide a maliciously crafted archive file to trigger the vulnerability.
Mitigation strategies for CVE-2016-4809 primarily focus on immediate version updates and defensive coding practices within affected applications. The most effective remediation involves upgrading to libarchive version 3.2.1 or later, where the vulnerability has been addressed through improved input validation and boundary checking mechanisms. Organizations should also implement additional defensive measures such as validating archive contents before processing, implementing resource limits on archive extraction operations, and employing sandboxed environments for archive processing tasks. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service attacks and represents a common exploitation pattern targeting library-level vulnerabilities in parsing components. System administrators should also consider implementing network-based intrusion detection systems that can identify suspicious archive processing patterns and monitor for potential exploitation attempts targeting this specific vulnerability class.