CVE-1999-1386 in Perl
Summary
by MITRE
Perl 5.004_04 and earlier follows symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack on the /tmp/perl-eaXXXXX file.
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability described in CVE-1999-1386 represents a critical security flaw in Perl versions 5.004_04 and earlier that stems from improper handling of symbolic links during script execution. This issue manifests when Perl processes scripts using the -e command line option, which executes Perl code directly from the command line. The vulnerability arises from Perl's failure to properly validate or sanitize the temporary files it creates during execution, specifically the /tmp/perl-eaXxxxxx file that serves as a temporary storage location for the executed code.
The technical implementation of this flaw involves Perl's use of symbolic links without adequate security checks when creating temporary files for execution. When a local user executes a Perl script with the -e option, Perl generates a temporary file in the /tmp directory to store the script content. However, due to insufficient validation, an attacker can create a symbolic link with the same name as the temporary file, causing Perl to write the script content to a location controlled by the attacker instead of the intended temporary location. This creates a classic race condition vulnerability where the attacker can manipulate the file system to redirect the script execution to overwrite arbitrary files on the system.
The operational impact of this vulnerability is significant as it allows local users to potentially overwrite critical system files, configuration files, or files owned by other users. The attack vector requires local system access but does not require special privileges beyond what a regular user already possesses. This makes the vulnerability particularly dangerous in multi-user environments where attackers might exploit it to escalate privileges or corrupt system integrity. The vulnerability aligns with CWE-59, which describes improper handling of symbolic links, and demonstrates how improper file system operations can lead to privilege escalation and data corruption scenarios.
From a mitigation perspective, the primary solution involves updating to Perl versions 5.004_05 or later where this vulnerability has been addressed through proper temporary file handling and symbolic link validation. System administrators should also implement proper file system permissions and consider using secure temporary file creation methods that avoid predictable file names or locations. The vulnerability relates to ATT&CK technique T1059.006 which covers execution through Perl, and T1078 which covers valid accounts as it exploits local user privileges. Organizations should also implement monitoring for suspicious temporary file creation patterns and consider restricting access to the /tmp directory to prevent symlink attacks. The issue highlights the importance of proper sandboxing and temporary file handling in interpreted languages, particularly those that execute code from command-line arguments, and serves as a reminder of the security implications of race conditions in file system operations.