Source: cve@mitre.org
HP ypbind allows attackers with root privileges to modify NIS data.
CVE-1999-0312 exposes a critical vulnerability in HP's ypbind service, allowing attackers with root privileges to compromise Network Information Service (NIS) data. Successful exploitation grants attackers the ability to modify NIS data, potentially leading to complete system compromise and data exfiltration. This vulnerability, though old, remains a threat if legacy systems are still in use and unpatched.
Step 1: Initial Compromise: The attacker gains root-level access on a system within the network. This could be through a separate vulnerability, social engineering, or a weak password.
Step 2: NIS Client Configuration: The attacker configures a NIS client on the compromised system to point to the vulnerable ypbind server.
Step 3: Malicious Request Crafting: The attacker crafts a malicious NIS request, designed to modify specific NIS maps (e.g., passwd.byname, hosts.byname). This request is crafted with the intent to overwrite legitimate NIS data with attacker-controlled data.
Step 4: Request Injection: The attacker sends the crafted NIS request to the ypbind server.
Step 5: Data Modification: The ypbind service, due to its lack of proper authorization checks, processes the malicious request and overwrites the specified NIS maps with the attacker's data. This could include adding new users with elevated privileges, modifying existing user accounts, or redirecting network traffic.
Step 6: System Compromise: With control over NIS data, the attacker can then gain complete control over the systems that rely on the compromised NIS server.
The vulnerability lies within the ypbind service's handling of requests from clients. The root cause is a lack of proper input validation and authorization checks when processing NIS requests. Specifically, the service fails to adequately verify the source of requests or the integrity of the data being received. This allows a privileged attacker (e.g., someone with root access on a compromised machine) to craft malicious NIS requests that overwrite critical NIS data, such as user account information, password hashes, and host configurations. The flaw is not a specific technical issue like a buffer overflow or race condition, but rather a design flaw allowing unauthorized modification of critical data.
Due to the age of this vulnerability, it's unlikely to be directly targeted by sophisticated APTs. However, it could be leveraged by less sophisticated actors or used as part of a larger attack chain. It's also possible that this vulnerability is used by APTs as part of a legacy system compromise. This vulnerability is not listed on the CISA KEV.
Monitor NIS server logs for unusual activity, such as unexpected modifications to NIS maps.
Analyze network traffic for suspicious NIS requests, especially those originating from unexpected sources or containing unusual data.
Implement file integrity monitoring on critical NIS map files to detect unauthorized changes.
Review system logs for evidence of unauthorized root access or privilege escalation.
Use intrusion detection systems (IDS) configured to identify malicious NIS traffic patterns.
Patching: Apply the appropriate security patches provided by HP or the vendor of the operating system. This is the primary and most effective remediation step.
Network Segmentation: Isolate the NIS server from the rest of the network to limit the impact of a compromise.
Access Control: Implement strict access controls to the NIS server, limiting access to only authorized users and systems.
Least Privilege: Ensure that users and services operate with the minimum necessary privileges.
Monitor and Audit: Regularly monitor NIS server logs and audit NIS configuration files for any suspicious activity.
Migrate Away from NIS: Consider migrating to a more secure directory service, such as LDAP or Active Directory, if possible.