CVE-1999-1386 is a vulnerability affecting Perl versions 5.004_04 and earlier. The issue arises from Perl's behavior when executed with the -e option, which allows the execution of code provided directly on the command line. Specifically, Perl creates a temporary file named /tmp/perl-eaXXXXX during this process. The vulnerability occurs because Perl follows symbolic links when handling this temporary file. This behavior enables a local attacker to create a symbolic link pointing to an arbitrary file and then trigger Perl with the -e option. As a result, the attacker can overwrite arbitrary files on the system by redirecting the temporary file writes through the symbolic link. This is a classic symlink attack, categorized under CWE-59 (Improper Link Resolution Before File Access). The vulnerability requires local access with at least limited privileges (PR:L) but does not require user interaction (UI:N). Exploitation can lead to integrity compromise (I:H) without affecting confidentiality or availability. The CVSS 3.1 base score is 5.5, indicating a medium severity level. No patches are available for this vulnerability, and there are no known exploits in the wild. The vulnerability is historical, dating back to 1999, and affects older Perl versions that are generally considered obsolete today.

For European organizations, the impact of this vulnerability is primarily on systems that still run legacy Perl versions 5.004_04 or earlier. Such systems might exist in legacy environments, embedded systems, or specialized industrial control systems that have not been updated. The ability for a local user to overwrite arbitrary files can lead to privilege escalation, unauthorized modification of critical configuration files, or insertion of malicious code, potentially compromising system integrity. While the vulnerability does not directly affect confidentiality or availability, the integrity impact can facilitate further attacks or system misuse. Given the age of the vulnerability and the lack of known exploits, the practical risk is low for modern, well-maintained environments. However, organizations with legacy systems or insufficient patch management may still be vulnerable. The threat is local, so remote attackers cannot exploit it directly, limiting the attack surface. Nonetheless, insider threats or attackers with limited access could leverage this vulnerability to escalate privileges or maintain persistence.

Since no official patch is available for this vulnerability, mitigation must focus on compensating controls. European organizations should: 1) Identify and inventory all systems running Perl 5.004_04 or earlier, prioritizing those exposed to local untrusted users. 2) Upgrade Perl to a supported, patched version where this symlink behavior is corrected. 3) Restrict local user permissions to prevent unauthorized creation of symbolic links in /tmp or other temporary directories. 4) Implement strict filesystem permissions and mount options (e.g., noexec, nosymfollow where supported) on /tmp to prevent symlink exploitation. 5) Employ mandatory access controls (e.g., SELinux, AppArmor) to limit the ability of local users to modify critical files or create symlinks in sensitive directories. 6) Monitor filesystem changes and unusual activity related to /tmp/perl-ea* files to detect potential exploitation attempts. 7) Where upgrading is not feasible, consider isolating legacy systems from general user access and network exposure to reduce risk.