CVE-1999-1023 is a vulnerability found in the useradd utility of Solaris 7.0 (SunOS 5.7). The issue arises from improper interpretation of certain date formats specified in the "-e" (expiration date) argument when creating or modifying user accounts. The expiration date is intended to disable user accounts after a certain date, preventing further logins. However, due to incorrect parsing of the date format, the system may fail to recognize that an account has expired, thereby allowing users to continue logging in even after their account expiration date has passed. This flaw undermines the intended access control mechanism and can lead to unauthorized access by users whose accounts should have been disabled. The vulnerability is local (attack vector: local), requires low attack complexity, and does not require authentication, but it impacts confidentiality, integrity, and availability to a partial extent. No patches are available for this vulnerability, and there are no known exploits in the wild. The affected product is SunOS 5.7, which corresponds to Solaris 7.0, an older operating system version that is largely obsolete today.

For European organizations still running legacy Solaris 7.0 systems, this vulnerability could allow users with expired accounts to maintain access beyond their authorized period. This could lead to unauthorized access to sensitive systems and data, potentially compromising confidentiality and integrity. The ability to bypass account expiration controls may also facilitate insider threats or unauthorized persistence by former employees or contractors. While the impact is limited to organizations using this outdated OS version, any critical infrastructure or legacy systems relying on Solaris 7.0 could be at risk. Given the age of the vulnerability and the lack of patches, organizations may face challenges in remediation. The vulnerability's exploitation does not require authentication, increasing the risk if local access is obtained. However, the overall risk is mitigated by the rarity of Solaris 7.0 usage in modern environments.

Since no official patches are available for this vulnerability, organizations should consider the following specific mitigation steps: 1) Upgrade or migrate from Solaris 7.0 to a supported and patched version of Solaris or another modern operating system to eliminate the vulnerability entirely. 2) Implement strict account management policies, including manual verification of account expiration and disabling accounts through alternative mechanisms such as centralized directory services (e.g., LDAP) that enforce expiration independently of the local useradd utility. 3) Restrict local access to Solaris 7.0 systems to trusted personnel only, minimizing the risk of exploitation. 4) Monitor login activities and audit account usage to detect any anomalous logins from expired accounts. 5) If upgrading is not immediately feasible, consider disabling or restricting the use of the "-e" option in useradd or replacing user management scripts with custom solutions that correctly enforce expiration dates. 6) Employ compensating controls such as multi-factor authentication and network segmentation to limit the impact of unauthorized access.