CVE-2008-4579 in cman
Summary
by MITRE
The (1) fence_apc and (2) fence_apc_snmp programs, as used in (a) fence 2.02.00-r1 and possibly (b) cman, when running in verbose mode, allows local users to append to arbitrary files via a symlink attack on the apclog temporary file.
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Analysis
by VulDB Data Team • 08/20/2019
The vulnerability identified as CVE-2008-4579 affects the fence_apc and fence_apc_snmp programs within the fence 2.02.00-r1 software package and potentially the cman cluster management system. This issue represents a classic symlink attack vulnerability that exploits improper handling of temporary files during verbose logging operations. The flaw specifically manifests when these programs execute in verbose mode, creating conditions where local attackers can manipulate file system permissions and create symbolic links to target arbitrary files within the system.
The technical implementation of this vulnerability stems from the insecure temporary file creation mechanism used by the fence_apc and fence_apc_snmp programs. When operating in verbose mode, these programs generate log output to a temporary file named apclog, but they fail to properly validate or secure this temporary file before writing to it. An attacker with local access can create a symbolic link named apclog in the program's working directory that points to any target file on the system. When the program executes and attempts to write to what it believes is a temporary file, it actually writes to the target file specified by the symbolic link, enabling arbitrary file modification or creation.
This vulnerability operates under the broader category of insecure temporary file handling as classified by CWE-377, specifically CWE-378 which addresses the creation of temporary files with insecure permissions. The attack vector involves a local privilege escalation scenario where an unprivileged user can leverage the program's verbose logging functionality to gain write access to files that would normally be protected from modification. The operational impact extends beyond simple file corruption as attackers can potentially overwrite critical system files, inject malicious content into log files, or manipulate program behavior through strategic file targeting.
The exploitation of this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1548.001 for abuse of privileges, as it enables local users to gain elevated access through file system manipulation. The vulnerability affects systems running the affected fence software versions and potentially impacts cluster management environments where cman is utilized, making it particularly concerning for high-availability and fault-tolerant systems. Organizations using these components should consider the broader implications for system integrity and audit trail reliability, as log files may become corrupted or manipulated through this attack vector.
Mitigation strategies include implementing proper temporary file creation mechanisms that use secure file creation patterns such as creating files with restrictive permissions and using atomic operations to prevent symlink attacks. The recommended approach involves modifying the fence programs to use secure temporary file creation functions that prevent the creation of symbolic links in the temporary file path, or ensuring that the temporary file is created in a secure location with appropriate permissions. Additionally, system administrators should disable verbose logging modes when not actively troubleshooting, and implement proper file system permissions to prevent unauthorized symbolic link creation in directories where these programs operate. The vulnerability demonstrates the importance of secure coding practices and proper input validation in system components that handle file operations, particularly in cluster management and high-availability systems where reliability and security are paramount.