CVE-2008-5155 in smsclient
Summary
by MITRE
mail2sms.sh in smsclient 2.0.8z allows local users to overwrite arbitrary files via a symlink attack on a (1) /tmp/header.##### or (2) /tmp/body.##### temporary file, or append data to arbitrary files via a symlink attack on the (3) /tmp/sms.log temporary file.
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Analysis
by VulDB Data Team • 10/14/2018
The vulnerability described in CVE-2008-5155 represents a critical file system permission and race condition issue within the smsclient 2.0.8z package, specifically affecting the mail2sms.sh script. This flaw enables local attackers to exploit weak temporary file handling mechanisms and manipulate file system operations through symbolic link attacks. The vulnerability stems from the script's improper handling of temporary files in the /tmp directory, creating opportunities for privilege escalation and data manipulation. The affected temporary files include header.#####, body.#####, and sms.log, all of which are susceptible to symbolic link attacks due to insufficient validation of file existence and permissions before file operations.
The technical exploitation of this vulnerability involves a classic race condition attack pattern where an attacker creates symbolic links to target files before the mail2sms.sh script processes them. When the script creates or modifies temporary files in /tmp without proper security checks, it becomes vulnerable to attackers who can establish symbolic links pointing to sensitive system files. The attacker can either overwrite existing files with malicious content or append data to arbitrary files, potentially compromising system integrity and confidentiality. This type of vulnerability falls under CWE-377: Insecure Temporary Files and CWE-378: Creation of Temporary Files With Insecure Permissions, both of which are well-documented weaknesses in software security practices.
The operational impact of this vulnerability is significant as it allows local users to gain unauthorized access to system resources and potentially escalate privileges. Attackers could use this vulnerability to modify system logs, overwrite critical configuration files, or inject malicious content into the smsclient functionality. The attack vector is particularly dangerous because it requires minimal privileges and can be executed by any local user with access to the system. This vulnerability directly impacts the principle of least privilege and can compromise the integrity of the entire smsclient system, potentially affecting SMS communication services and data processing workflows. The attack can be executed through standard Unix file system operations and does not require specialized tools or complex exploitation techniques.
Mitigation strategies for CVE-2008-5155 involve implementing proper temporary file handling practices and ensuring that all temporary files are created with secure permissions and atomic operations. System administrators should modify the mail2sms.sh script to use secure temporary file creation methods such as mktemp with appropriate permissions, or implement proper file existence checks before file operations. The solution should include setting restrictive file permissions for temporary files and ensuring that the script runs with minimal necessary privileges. Additionally, regular security audits and code reviews should be conducted to identify similar vulnerabilities in other system components. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1548.001 for Abuse of System Permissions, demonstrating how insecure file handling can enable broader system compromise. Organizations should also consider implementing file system monitoring and integrity checking mechanisms to detect unauthorized modifications to critical system files.