CVE-2017-6512 in File-Path Module
Summary
by MITRE
Race condition in the rmtree and remove_tree functions in the File-Path module before 2.13 for Perl allows attackers to set the mode on arbitrary files via vectors involving directory-permission loosening logic.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-6512 represents a significant race condition flaw within the File-Path module for Perl versions prior to 2.13. This issue stems from improper handling of directory permissions during file removal operations, specifically affecting the rmtree and remove_tree functions that are commonly used for recursive directory deletion. The core problem manifests when attackers can manipulate the timing of file system operations to exploit a window where directory permissions are temporarily loosened, allowing malicious actors to gain unauthorized access to files that should remain protected.
The technical implementation of this vulnerability involves a classic race condition scenario where the File-Path module performs a sequence of operations that create a temporal gap between permission checks and actual file system modifications. During the execution of rmtree and remove_tree functions, the module first checks directory permissions and then proceeds with deletion operations. This gap in logic allows attackers to exploit the window where directory permissions are temporarily modified, enabling them to change file modes on arbitrary files that would normally be protected by stricter permission controls. The flaw specifically targets the directory-permission loosening logic that is designed to handle recursive directory removal but becomes exploitable when attackers can manipulate the file system state between permission checks.
From an operational perspective, this vulnerability poses a serious threat to system security as it allows attackers to escalate privileges and potentially modify critical system files or sensitive data. The impact extends beyond simple file access, as attackers can leverage this race condition to alter file permissions, modify executable files, or even inject malicious code into system directories. The vulnerability is particularly dangerous in environments where Perl scripts are used for system administration tasks or where file permissions are strictly enforced as part of security policies. The race condition can be triggered through various attack vectors involving directory manipulation and timing attacks that exploit the temporal gap in the permission handling logic.
Security professionals should note that this vulnerability aligns with CWE-367, which addresses time-of-check to time-of-use (TOCTOU) race conditions, and relates to ATT&CK technique T1068 which involves privilege escalation through race conditions. The recommended mitigations include immediate upgrading to File-Path version 2.13 or later where the race condition has been patched, implementing proper file system permission controls, and conducting thorough code reviews of any custom Perl scripts that utilize recursive directory removal functions. Organizations should also consider implementing monitoring solutions to detect suspicious file permission changes and establish robust patch management processes to ensure all Perl modules are kept up to date with security fixes. Additionally, system administrators should review and restrict the use of recursive directory removal functions in security-sensitive contexts where such vulnerabilities could be exploited to compromise system integrity.