CVE-2008-5366 in ppp
Summary
by MITRE
The postinst script in ppp 2.4.4rel on Debian GNU/Linux allows local users to overwrite arbitrary files via a symlink attack on the (1) /tmp/probe-finished or (2) /tmp/ppp-errors temporary file.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/19/2018
The vulnerability identified as CVE-2008-5366 resides within the postinst script of the ppp package version 2.4.4rel on Debian GNU/Linux systems. This issue represents a classic symlink attack scenario that exploits insecure temporary file handling practices. The vulnerability specifically targets two temporary files located at /tmp/probe-finished and /tmp/ppp-errors which are created during the package installation process. When the postinst script executes, it creates these temporary files without proper security checks, making them susceptible to manipulation by local users who can establish symbolic links to overwrite critical system files or inject malicious content.
The technical flaw manifests through the lack of proper file permission validation and atomic file creation mechanisms within the postinst script. Local attackers can create symbolic links with the same names as the temporary files before the installation process completes, effectively redirecting the script's file operations to arbitrary locations on the filesystem. This type of vulnerability falls under the CWE-377 weakness category, specifically CWE-377: Insecure Temporary File, which is classified as a high-risk vulnerability due to its potential for privilege escalation and system compromise. The attack vector leverages the principle of least privilege violation, where the installation process creates files with predictable names in world-writable directories without proper security controls.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can enable local users to gain elevated privileges or disrupt system operations. An attacker who successfully executes this symlink attack could potentially overwrite system configuration files, log files, or even binaries with malicious content, leading to persistent backdoors or complete system compromise. The vulnerability is particularly dangerous in multi-user environments where less privileged users might exploit this weakness to escalate their privileges or corrupt system integrity. According to ATT&CK framework, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1068 (Local Privilege Escalation) techniques, as it provides a mechanism for privilege escalation through insecure file handling.
Mitigation strategies for CVE-2008-5366 should focus on immediate package updates and system hardening measures. The most effective solution involves upgrading to a patched version of the ppp package where the installation script properly validates file creation operations and uses secure temporary file creation methods. System administrators should also implement proper file permissions and ensure that temporary directories are not world-writable. Additional mitigations include monitoring for suspicious symbolic link creation in temporary directories, implementing mandatory access controls through SELinux or AppArmor, and conducting regular security audits to identify similar insecure temporary file handling patterns in other system components. The vulnerability demonstrates the critical importance of secure coding practices in installation scripts and highlights the need for comprehensive security testing of system-level packages.