Source: cve@mitre.org
In SunOS, NFS file handles could be guessed, giving unauthorized access to the exported file system.
SunOS systems are vulnerable to unauthorized access via NFS file handle guessing, allowing attackers to bypass access controls and potentially gain complete control of the exported file system. This vulnerability, dating back to 1991, highlights the importance of robust security practices and the need to patch legacy systems. Exploitation can lead to data breaches, system compromise, and denial of service.
Step 1: Reconnaissance: The attacker identifies a SunOS system exporting an NFS file system.
Step 2: File Handle Guessing/Brute-Force: The attacker attempts to guess or brute-force valid NFS file handles. This could involve analyzing the file system structure, using known file handle patterns, or trying a range of possible values.
Step 3: Crafting NFS Requests: The attacker crafts NFS requests using the guessed file handles, targeting specific files or directories.
Step 4: Accessing Unauthorized Files: If the guessed file handle is valid, the attacker gains unauthorized access to the corresponding file or directory, bypassing the intended access controls.
Step 5: Privilege Escalation (Potential): Depending on the accessed files, the attacker might be able to escalate privileges or gain further access to the system.
The vulnerability lies in the design of the NFS file handle generation mechanism within SunOS. The file handles, which are used to identify files on the server, were predictable or guessable. This predictability allowed attackers to craft requests with file handles that corresponded to files they were not authorized to access. The root cause is a lack of sufficient entropy in the file handle generation algorithm, making it susceptible to brute-force attacks or educated guessing. The system failed to properly validate the file handle provided in client requests, trusting the client's provided handle. This allowed attackers to bypass access control mechanisms and access sensitive data. The vulnerability is not a buffer overflow or race condition, but rather a design flaw in the file handle generation and validation process.
While no specific APT groups are directly associated with this very old CVE, any threat actor targeting legacy systems could potentially exploit this vulnerability. The risk is higher for organizations that maintain old SunOS systems. This CVE is NOT listed in the CISA KEV catalog.
Monitor NFS server logs for suspicious activity, such as a large number of failed access attempts or requests for files that should not be accessed by the client.
Analyze network traffic for unusual NFS requests, especially those with file handles that appear to be generated randomly or are outside the expected range.
Examine system logs for unauthorized access attempts or file access events.
Implement file integrity monitoring to detect changes to critical system files.
Patching: Apply the latest security patches for the SunOS operating system. This is the most effective solution.
Disable NFS Exporting: If NFS is not required, disable NFS exporting to eliminate the attack surface.
Restrict NFS Access: If NFS is required, restrict access to only trusted clients and networks.
Implement Strong Authentication: Use strong authentication mechanisms, such as Kerberos, to secure NFS access.
Regular Security Audits: Conduct regular security audits to identify and address vulnerabilities.
Network Segmentation: Isolate SunOS systems on a separate network segment to limit the impact of a potential breach.
File Handle Obfuscation: While not a direct fix for this CVE, modern NFS implementations use more robust file handle generation algorithms.