CVE-2014-3856 in fish
Summary
by MITRE
The funced function in fish (aka fish-shell) 1.23.0 before 2.1.1 does not properly create temporary files, which allows local users to gain privileges via a temporary file with a predictable name.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability identified as CVE-2014-3856 affects the fish shell version 1.23.0 and earlier versions before 2.1.1, specifically within the funced function implementation. This flaw represents a classic temporary file creation vulnerability that enables local privilege escalation attacks through predictable filename exploitation. The issue stems from the improper handling of temporary file generation mechanisms within the shell's function editing functionality, creating a security weakness that adversaries can leverage to execute malicious code with elevated privileges.
The technical root cause of this vulnerability lies in the predictable naming convention used for temporary files created by the funced function. When users attempt to edit shell functions through this interface, the system generates temporary files with known or easily guessable names, which creates an opportunity for privilege escalation. This type of vulnerability aligns with CWE-377, which addresses insecure temporary file creation practices, and falls under the broader category of insecure file handling within shell environments. The predictable naming scheme allows malicious users to create symbolic links or replace existing temporary files with crafted content before the legitimate process accesses them.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and unauthorized access to sensitive data. Attackers can exploit this weakness by creating malicious temporary files with the same predictable names that the funced function generates, effectively intercepting or manipulating the shell's function editing process. This vulnerability particularly affects systems where users have access to the fish shell but lack administrative privileges, as it provides a vector for privilege elevation that can lead to complete system compromise. The attack surface is significant in multi-user environments where shell functionality is frequently used.
Mitigation strategies for CVE-2014-3856 should prioritize immediate patching of affected fish shell versions to 2.1.1 or later, which addresses the improper temporary file creation mechanism. System administrators should also implement proper file permissions and access controls to limit user privileges, particularly when shell functions are edited. The implementation of secure temporary file creation practices, such as using unique identifiers or random naming schemes, can prevent similar vulnerabilities from occurring in other software components. Additionally, monitoring for suspicious file creation patterns and implementing proper intrusion detection measures can help identify potential exploitation attempts. This vulnerability demonstrates the critical importance of secure coding practices in shell environments and aligns with ATT&CK technique T1068, which covers privilege escalation through local exploits, making it essential for security teams to address such weaknesses proactively.