CVE-2015-1197 in cpio
Summary
by MITRE
cpio 2.11, when using the --no-absolute-filenames option, allows local users to write to arbitrary files via a symlink attack on a file in an archive.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2015-1197 affects the cpio utility version 2.11 and specifically manifests when the --no-absolute-filenames option is employed during archive extraction operations. This flaw represents a classic symlink attack vector that exploits the trust relationship between the archive extraction process and file system permissions. The cpio utility, widely used for creating and extracting archive files in unix-like systems, processes archive contents by extracting files to their specified locations while maintaining the original file attributes and paths. When the --no-absolute-filenames option is enabled, cpio strips leading slashes from file paths, which is intended to prevent absolute path traversal during extraction. However, this behavior creates a dangerous condition when the archive contains symbolic links that point to arbitrary file locations.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious archive containing symbolic links that reference files outside the intended extraction directory. During the extraction process, cpio follows these symbolic links and creates files at the target locations specified by the symlinks, bypassing normal file system permission checks and directory boundaries. This behavior stems from a fundamental flaw in how cpio handles symbolic links when the --no-absolute-filenames option is active, creating a race condition where the utility does not properly validate the target locations of symbolic links against the extraction context. The vulnerability is categorized under CWE-59, which specifically addresses improper handling of symbolic links, and aligns with ATT&CK technique T1059.007 for execution through command and scripting interpreter, particularly when attackers leverage the compromised extraction process to gain unauthorized file system access.
The operational impact of CVE-2015-1197 extends beyond simple file system manipulation, as it can enable attackers to overwrite critical system files, inject malicious code into existing binaries, or create backdoor access points within the system. Local users who have the ability to create or modify archives can exploit this vulnerability to write arbitrary content to files they would normally not have permission to modify, effectively elevating their privileges within the context of the extraction operation. This vulnerability particularly affects systems where cpio is used for automated archive processing, such as package managers, backup systems, or software deployment tools that automatically extract archives without proper validation of archive contents. The attack scenario typically involves an attacker who can influence the contents of an archive that will be processed by a vulnerable cpio version, making it especially dangerous in environments where users can submit or upload archives for processing. The vulnerability is classified as a privilege escalation vector under ATT&CK framework, specifically targeting the execution and persistence techniques that allow attackers to gain unauthorized access to system resources.
Mitigation strategies for CVE-2015-1197 require immediate patching of affected cpio versions to the latest releases that address this symbolic link handling flaw. Organizations should implement strict archive validation procedures that verify the contents of archives before processing, particularly when dealing with user-submitted or externally sourced archives. The use of the --no-absolute-filenames option should be carefully evaluated and potentially disabled in environments where archive contents cannot be fully trusted. System administrators should consider implementing additional security controls such as restricted extraction directories, mandatory access controls, and monitoring for unauthorized file system modifications during archive extraction processes. Security teams should also establish procedures to audit and validate archive contents, ensuring that symbolic links within archives are properly sanitized and do not point to sensitive system locations. The vulnerability highlights the importance of proper input validation and secure file handling practices in system utilities, particularly those that operate with elevated privileges during file system operations. Organizations should also consider implementing automated scanning tools to identify systems running vulnerable cpio versions and ensure that all systems are updated to versions that properly handle symbolic links during archive extraction operations.