CVE-2008-4192 in cman
Summary
by MITRE
The pserver_shutdown function in fence_egenera in cman 2.20080629 and 2.20080801 allows local users to overwrite arbitrary files via a symlink attack on the /tmp/eglog temporary file.
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Analysis
by VulDB Data Team • 08/20/2019
The vulnerability identified as CVE-2008-4192 resides within the fence_egenera component of the cman clustering software version 2.20080629 and 2.20080801. This issue represents a critical security flaw that enables local attackers to manipulate the system through a carefully crafted symlink attack targeting a temporary file location. The vulnerability specifically affects the pserver_shutdown function which handles the shutdown process for egenera fence devices within a clustered environment. The flaw manifests when the system creates temporary files without proper security checks, allowing malicious users to establish symbolic links that redirect file operations to unintended targets.
The technical implementation of this vulnerability follows a classic race condition pattern where the temporary file is created with predictable naming and insecure permissions. The /tmp/eglog file path serves as the attack vector where a local user can create a symbolic link with the same name before the legitimate process creates the actual file. This timing window enables the attacker to control what gets written to the target location, potentially allowing arbitrary file overwrite operations. The vulnerability is classified under CWE-367 which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, where the security check occurs at a different time than the actual operation, creating an exploitable window.
From an operational perspective, this vulnerability poses significant risks to clustered computing environments where cman is deployed. Local users with minimal privileges can leverage this flaw to overwrite critical system files, potentially leading to privilege escalation, data corruption, or system instability. The impact extends beyond simple file manipulation as attackers could target configuration files, binary executables, or sensitive log data. In enterprise environments, this vulnerability could allow malicious insiders or compromised low-privilege accounts to gain deeper access to the cluster infrastructure, undermining the security model of the entire distributed system.
The attack vector aligns with ATT&CK technique T1059.007 for executing malicious code through shell commands and T1548.001 for privilege escalation. The exploit requires local access to the system but does not need network connectivity, making it particularly dangerous in environments where local security is assumed. Mitigation strategies include implementing proper file creation atomicity with secure temporary file handling, using umask settings to prevent insecure file permissions, and ensuring that temporary files are created with unique names or in secure directories. The most effective remediation involves upgrading to patched versions of cman where the pserver_shutdown function properly handles temporary file creation without race conditions, and where the system employs secure file handling practices that prevent symlink attacks on temporary files.