CVE-2018-12015 in macOS
Summary
by MITRE
In Perl through 5.26.2, the Archive::Tar module allows remote attackers to bypass a directory-traversal protection mechanism, and overwrite arbitrary files, via an archive file containing a symlink and a regular file with the same name.
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Analysis
by VulDB Data Team • 08/08/2023
The vulnerability identified as CVE-2018-12015 affects the Archive::Tar module in Perl versions up to 5.26.2, representing a critical directory traversal flaw that undermines fundamental security protections designed to prevent arbitrary file overwrites. This vulnerability specifically targets the module's handling of archive files that contain both symbolic links and regular files with identical names, creating a race condition that allows attackers to bypass intended security mechanisms.
The technical flaw stems from how Archive::Tar processes archive entries during extraction operations. When an archive contains a symbolic link followed by a regular file with the same name, the module fails to properly validate the sequence of operations, enabling attackers to manipulate the extraction process. The vulnerability manifests when the system processes the symlink first, creating a symbolic link that points to a target location, followed by the regular file operation that overwrites the target file with malicious content. This behavior violates the expected security model that should prevent directory traversal attacks by ensuring that file operations occur within designated boundaries.
The operational impact of this vulnerability is severe as it allows remote attackers to perform arbitrary file overwrites on systems running vulnerable Perl versions. Attackers can leverage this flaw to overwrite critical system files, configuration files, or application data, potentially leading to privilege escalation, system compromise, or denial of service conditions. The vulnerability is particularly dangerous in environments where Perl applications handle untrusted archive files, such as web applications processing user-uploaded files or automated systems extracting archive content from external sources. This issue directly relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and represents a classic example of a race condition vulnerability in file system operations.
The exploitation of this vulnerability requires minimal prerequisites and can be executed remotely through maliciously crafted archive files. Attackers need only create an archive containing a symbolic link entry followed by a regular file entry with the same name, where the symbolic link points to a target file they wish to overwrite. This attack vector is particularly insidious because it can be concealed within legitimate archive files, making detection more difficult. The vulnerability aligns with ATT&CK technique T1059.007, which describes the use of scripting languages for execution, and T1203, which covers the exploitation of software vulnerabilities for privilege escalation. Organizations should immediately update their Perl installations to versions 5.26.3 or later, where the Archive::Tar module has been patched to properly validate file operations and prevent the race condition that enables this attack. Additionally, implementing proper input validation for archive files, restricting file extraction permissions, and monitoring for suspicious file operations can help mitigate the risk associated with this vulnerability.