CVE-1999-1383 is a medium-severity local privilege escalation vulnerability affecting older versions of the GNU bash shell (versions before 1.14.7) and the tcsh shell version 6.05. The vulnerability arises from the way these shells handle directory names containing shell metacharacters, specifically the back-tick (`). When the shell prompt string (PS1) uses the \w option to display the current working directory, it expands the directory name. If the directory name contains back-ticks, the shell executes the commands enclosed within them during this expansion. This behavior allows a local user to craft directory names that include malicious commands, which are then executed with the privileges of the user running the shell. Since the vulnerability requires local access and the presence of vulnerable shell versions, exploitation is limited to local users who can create or rename directories. The vulnerability impacts confidentiality, integrity, and availability because arbitrary commands can be executed, potentially leading to privilege escalation and system compromise. The CVSS score of 4.6 reflects a medium severity, considering the local access vector, low attack complexity, no authentication requirement, and partial impact on confidentiality, integrity, and availability. No patches are available for these legacy versions, and no known exploits in the wild have been reported. The underlying weakness corresponds to CWE-264, which relates to permissions, privileges, and access controls mismanagement.

For European organizations, the impact of this vulnerability largely depends on the presence of legacy systems running the affected bash or tcsh versions. While modern Linux distributions have long since updated bash beyond version 1.14.7, some embedded systems, legacy servers, or specialized industrial control systems might still run outdated shells. If exploited, a local attacker could escalate privileges, potentially gaining root access, leading to unauthorized data access, system manipulation, or disruption of services. This could compromise sensitive information, disrupt business operations, and damage organizational reputation. Given the local access requirement, the threat is more relevant in environments where multiple users share systems or where attackers have already gained limited access and seek privilege escalation. European organizations with critical infrastructure, research institutions, or legacy IT environments should be particularly cautious. The lack of known exploits reduces immediate risk, but the vulnerability remains a concern for systems that have not been updated in decades.

Since no official patches exist for these outdated shell versions, the primary mitigation is to upgrade to a modern, supported version of bash (1.14.7 or later) or tcsh beyond version 6.05. Organizations should conduct thorough audits to identify any systems running these legacy shells, including embedded devices and legacy servers. For systems where upgrading is not feasible, restricting local user access and implementing strict access controls can reduce exploitation risk. Additionally, monitoring for suspicious directory names containing shell metacharacters and employing file system integrity tools can help detect attempts to exploit this vulnerability. Employing security policies that limit the use of shell prompts with the \w option or customizing PS1 to avoid vulnerable expansions can also mitigate risk. Finally, educating system administrators about legacy vulnerabilities and encouraging timely patch management is essential to prevent exploitation.