Source: cve@mitre.org
rpc.pwdauthd in SunOS 4.1.1 and earlier does not properly prevent remote access to the daemon, which allows remote attackers to obtain sensitive system information.
SunOS 4.1.1 and earlier systems are vulnerable to remote information disclosure due to a flaw in the rpc.pwdauthd daemon, allowing attackers to remotely access and extract sensitive system information. This vulnerability can lead to credential theft and system compromise, potentially enabling further attacks. Exploitation is relatively straightforward and poses a significant risk to legacy systems.
Step 1: Reconnaissance: The attacker identifies a target system running a vulnerable version of SunOS (4.1.1 or earlier). This can be done through port scanning (e.g., checking for RPC services) and banner grabbing.
Step 2: Request Construction: The attacker crafts a malicious RPC request specifically designed to query rpc.pwdauthd for sensitive information. The exact request format depends on the specific RPC call being exploited.
Step 3: Request Delivery: The attacker sends the crafted RPC request to the target system's rpc.pwdauthd daemon via the network.
Step 4: Information Retrieval: The vulnerable rpc.pwdauthd daemon processes the malicious request without proper authentication or authorization. It then retrieves and transmits the requested sensitive information (e.g., user account details) back to the attacker.
Step 5: Data Analysis: The attacker receives the sensitive information and analyzes it to gain further access to the system or other connected systems.
The vulnerability stems from rpc.pwdauthd failing to properly restrict access to its functionality. Specifically, the daemon does not implement adequate authentication or authorization mechanisms, allowing unauthenticated remote requests. This lack of access control permits attackers to query the daemon for sensitive information, such as user account details, password hashes (if stored), and other system configuration data. The root cause is a design flaw where the daemon trusts all incoming requests without proper validation, leading to unauthorized information disclosure. This is not a complex coding error like a buffer overflow, but rather a fundamental security oversight in the daemon's architecture.
Due to the age of the vulnerability and the systems it affects, it is unlikely that specific APTs or malware are actively targeting this vulnerability. However, any attacker with basic network skills could exploit this. This vulnerability is not listed on the CISA KEV as it is considered obsolete.
Network traffic analysis: Examine network traffic for RPC requests to port 111 (portmapper) and other RPC ports. Look for unusual RPC calls or requests to rpc.pwdauthd.
Log analysis: Review system logs (e.g., syslog) for suspicious activity related to RPC services or authentication failures. However, the lack of authentication in the vulnerable daemon makes logging less reliable.
Host-based intrusion detection systems (HIDS): If available on the legacy system, HIDS can be configured to monitor for changes to system files or suspicious process activity related to RPC services.
Isolate affected systems: The most effective remediation is to isolate any remaining vulnerable systems from the network to prevent remote access.
Upgrade or replace: The primary solution is to upgrade to a supported version of SunOS or, preferably, replace the outdated system with a modern operating system. This is the only truly effective long-term solution.
Disable the service: If upgrading is not possible, disable the rpc.pwdauthd service. This will prevent remote access to the daemon. However, this may impact other services that rely on it.
Implement network segmentation: If the system cannot be upgraded, segment the network to limit the attack surface. Place the vulnerable system in a separate network segment and restrict access to it.
Monitor network traffic: Implement network monitoring to detect any suspicious RPC traffic.