CVE-2001-1494 in util-linux
Summary
by MITRE
script command in the util-linux package before 2.11n allows local users to overwrite arbitrary files by setting a hardlink from the typescript log file to any file on the system, then having root execute the script command.
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Analysis
by VulDB Data Team • 09/05/2019
The vulnerability described in CVE-2001-1494 resides within the script command functionality of the util-linux package version 2.11n and earlier. This issue represents a classic privilege escalation flaw that leverages symbolic link manipulation to enable local users to gain unauthorized write access to system files. The vulnerability specifically targets the script command's handling of log file creation and management, where it fails to properly validate or sanitize the destination file paths, creating an exploitable race condition scenario.
The technical flaw manifests when a local attacker creates a hardlink from a target file to the script command's default log file location, typically named typescript. When root executes the script command, the system attempts to create the log file at the specified location, but due to the hardlink relationship, the command actually writes to the attacker-controlled target file instead of the intended log file. This behavior stems from a lack of proper file access validation and atomic file creation mechanisms within the script command implementation, allowing attackers to redirect write operations to arbitrary locations within the filesystem.
The operational impact of this vulnerability extends beyond simple file overwriting, as it enables attackers to modify critical system files, configuration data, or even executable binaries. The vulnerability is particularly dangerous because it requires only local user privileges to exploit, yet can result in privilege escalation when root executes the script command. This creates a significant security risk in multi-user environments where users may have legitimate reasons to execute the script command but lack proper file system permissions. The vulnerability can be exploited to modify system files, inject malicious code, or corrupt critical data, potentially leading to complete system compromise or persistent backdoor access.
Mitigation strategies for this vulnerability include upgrading to util-linux version 2.11n or later, where the script command properly handles file creation and validation. System administrators should also implement proper file access controls and monitor for suspicious hardlink creation patterns, particularly in directories where privileged commands are executed. The vulnerability aligns with CWE-377: Insecure Temporary File and CWE-276: Incorrect Permission Assignment, representing poor file handling security practices that have been addressed through improved file creation and validation mechanisms. Organizations should also consider implementing the principle of least privilege for command execution, ensuring that only authorized users can execute potentially dangerous commands like script, and regularly auditing system permissions and file access patterns to detect potential exploitation attempts. This vulnerability demonstrates the importance of proper input validation and atomic file operations in security-critical system utilities, as outlined in various ATT&CK techniques related to privilege escalation and persistence mechanisms.