CVE-2015-8607 in PathTools
Summary
by MITRE
The canonpath function in the File::Spec module in PathTools before 3.62, as used in Perl, does not properly preserve the taint attribute of data, which might allow context-dependent attackers to bypass the taint protection mechanism via a crafted string.
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Analysis
by VulDB Data Team • 07/05/2018
The CVE-2015-8607 vulnerability resides within the File::Spec module of PathTools, a core Perl library that handles file path manipulation across different operating systems. This flaw specifically affects versions prior to 3.62 and represents a critical weakness in Perl's taint mode protection mechanism. The vulnerability manifests in the canonpath function, which is responsible for canonicalizing file paths by removing redundant components and normalizing path separators. When processing certain input strings, the function fails to properly maintain the taint attribute that Perl's taint mode imposes on data originating from external sources. This taint attribute serves as a fundamental security feature that prevents untrusted data from being used in potentially dangerous operations such as system calls, file operations, or command execution.
The technical nature of this vulnerability stems from improper handling of tainted data within the canonpath function's internal processing logic. In Perl's taint mode, data from external sources such as command-line arguments, environment variables, or file inputs is marked with a taint flag that should prevent its use in sensitive operations. However, when the canonpath function processes this tainted data, it inadvertently strips or fails to propagate the taint flag, effectively allowing attackers to bypass these security protections. The crafted strings that trigger this vulnerability typically involve complex path structures with special characters, symbolic links, or unusual path components that cause the function to behave unexpectedly and lose track of the taint state. This behavior creates a security loophole where attacker-controlled input can be transformed into untainted data that subsequently passes through Perl's security checks.
The operational impact of CVE-2015-8607 extends beyond simple path manipulation and represents a significant threat to applications that rely on Perl's taint protection for security. Systems running vulnerable versions of PathTools could be exploited by context-dependent attackers who craft malicious input strings to bypass taint mode protections, potentially leading to privilege escalation, arbitrary code execution, or unauthorized file access. Applications that process user-supplied file paths or filenames through Perl's File::Spec module are particularly vulnerable, especially when these applications operate in taint mode and rely on the security guarantees provided by this protection mechanism. The vulnerability is especially dangerous in web applications, system administration tools, or any Perl-based software that handles untrusted input and depends on taint mode to prevent injection attacks.
Mitigation strategies for CVE-2015-8607 primarily involve upgrading to PathTools version 3.62 or later, which contains the necessary patches to properly preserve taint attributes during path canonicalization. Organizations should prioritize updating their Perl environments and verifying that all applications using File::Spec are running on patched versions. Additionally, security practitioners should implement additional layers of protection including input validation, sandboxing, and runtime monitoring to detect potential exploitation attempts. The vulnerability aligns with CWE-250, which addresses "Execute Code with Unintended Privileges" and relates to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Perl" in attack chains where attackers attempt to bypass security controls through manipulation of interpreted languages. System administrators should also consider implementing network segmentation, privilege separation, and regular security audits to minimize the potential impact of such vulnerabilities in their environments.