CVE-2011-0702 in feh
Summary
by MITRE
The feh_unique_filename function in utils.c in feh before 1.11.2 might allow local users to overwrite arbitrary files via a symlink attack on a /tmp/feh_ temporary file.
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Analysis
by VulDB Data Team • 10/17/2021
The vulnerability identified as CVE-2011-0702 affects the feh image viewer software version 1.11.1 and earlier, presenting a significant security risk through improper temporary file handling. This flaw exists within the feh_unique_filename function located in the utils.c source file, where the software creates temporary files in the /tmp directory without adequate security measures to prevent symbolic link attacks. The issue arises from the predictable naming convention used for temporary files, which creates opportunities for local attackers to manipulate the file system through symlink manipulation.
The technical implementation of this vulnerability stems from the software's failure to properly validate or secure temporary file creation processes. When feh generates temporary files in /tmp with names like feh_ followed by a numeric identifier, attackers can create symbolic links with the same names in the target directory before the legitimate file creation process occurs. This race condition allows malicious users to redirect file operations to arbitrary locations on the file system, potentially enabling them to overwrite critical system files or inject malicious content into files that would normally be restricted to the application's legitimate use.
From an operational perspective, this vulnerability represents a local privilege escalation risk that can be exploited by any user with access to the system. The attack vector is particularly concerning because it does not require elevated privileges to execute, yet can potentially allow attackers to modify files that the application normally cannot access or modify. The impact extends beyond simple file overwrites to include potential data corruption, system instability, and information disclosure. Security researchers have classified this as a directory traversal or symlink attack vulnerability, which aligns with common attack patterns documented in the MITRE ATT&CK framework under techniques related to privilege escalation and file system manipulation.
The vulnerability directly corresponds to CWE-377, which addresses the insecure handling of temporary files, and CWE-378, which covers the creation of temporary files with insecure permissions. These weaknesses create conditions where attackers can exploit predictable naming patterns and race conditions to gain unauthorized access to system resources. The security implications extend to potential information disclosure when attackers can manipulate temporary files to read or modify data that would normally be protected. Organizations using feh image viewer software should prioritize updating to version 1.11.2 or later, where the vulnerability has been addressed through improved temporary file handling mechanisms that prevent symlink attacks and implement proper file creation security measures. Additional mitigations include restricting write permissions to the /tmp directory and implementing proper file system hardening measures to prevent unauthorized symbolic link creation.