CVE-2016-3992 in cronic
Summary
by MITRE
cronic before 3 allows local users to write to arbitrary files via a symlink attack on a (1) cronic.out.$$, (2) cronic.err.$$, or (3) cronic.trace.$$ file in /tmp.
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Analysis
by VulDB Data Team • 10/06/2024
The vulnerability identified as CVE-2016-3992 affects the cronic utility version 3 and earlier, presenting a significant local privilege escalation risk through symbolic link attacks. This flaw resides in the temporary file handling mechanism of cronic, which is commonly used for logging and error reporting in Unix-like systems. The vulnerability specifically targets the temporary files cronic.out.$$, cronic.err.$$, and cronic.trace.$$ located in the /tmp directory, where $$ represents the process ID of the cronic execution. The root cause of this issue stems from insufficient validation of temporary file creation, allowing malicious local users to exploit the predictable naming convention and race condition inherent in the file creation process.
The technical exploitation of this vulnerability occurs through a carefully orchestrated symlink attack that leverages the predictable naming pattern of temporary files. When cronic executes, it creates temporary files with specific naming conventions in the /tmp directory, but fails to properly validate whether these files already exist or are symbolic links. An attacker can pre-create symbolic links with the exact same names in the /tmp directory, causing cronic to write sensitive data to arbitrary locations on the filesystem. This technique, classified under CWE-377 as insecure temporary file creation, allows attackers to redirect output from cronic's logging mechanisms to sensitive system files or locations where they can execute code or gain unauthorized access. The vulnerability demonstrates a classic race condition pattern that violates proper file access control principles and represents a fundamental flaw in the utility's security design.
The operational impact of CVE-2016-3992 extends beyond simple file manipulation, potentially enabling attackers to compromise system integrity and confidentiality. Local users who can execute cronic with elevated privileges or those who have access to a system where cronic is run with higher privileges can leverage this vulnerability to write malicious content to critical system files, including configuration files, log files, or even binary executables. This capability aligns with ATT&CK technique T1059 for executing malicious code and T1070 for clearing logs, as attackers can manipulate cronic's output to hide their activities or establish persistence. The vulnerability is particularly dangerous in multi-user environments where users may have legitimate access to cronic but should not have write access to system-critical files, creating a privilege escalation vector that could allow attackers to gain unauthorized access to system resources.
Mitigation strategies for CVE-2016-3992 require immediate patching of affected cronic versions to address the underlying file creation vulnerability. Organizations should implement proper temporary file handling procedures that utilize secure file creation methods such as creating files with exclusive access permissions and verifying file ownership before writing. The solution should incorporate checks for existing files and symbolic links before temporary file creation, as recommended by secure coding practices and aligned with CWE-378 standards for secure temporary file creation. System administrators should also consider restricting access to the /tmp directory and implementing proper file system permissions that prevent unauthorized symbolic link creation. Additionally, monitoring for suspicious file creation patterns in /tmp and implementing automated security scanning tools can help detect exploitation attempts. The vulnerability highlights the importance of proper input validation and secure file handling practices, particularly in utilities that operate with elevated privileges or handle sensitive system information, emphasizing the need for comprehensive security testing and code review processes that address race condition vulnerabilities.