CVE-2004-0154 in nfs-utils
Summary
by MITRE
rpc.mountd in nfs-utils after 1.0.3 and before 1.0.6 allows attackers to cause a denial of service (crash) via an NFS mount of a directory from a client whose reverse DNS lookup name is different from the forward lookup name.
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Analysis
by VulDB Data Team • 06/27/2019
The vulnerability identified as CVE-2004-0154 affects the rpc.mountd daemon component within the nfs-utils package, specifically impacting versions between 1.0.3 and 1.0.6. This issue represents a classic denial of service weakness that exploits inconsistencies in DNS resolution mechanisms to disrupt network file sharing services. The rpc.mountd daemon serves as a crucial component in the Network File System architecture, responsible for managing NFS mount requests and maintaining the mapping between client hosts and their mounted filesystems. When an NFS client attempts to mount a directory, the rpc.mountd service performs reverse DNS lookups to verify client identity and permissions, creating a potential attack vector through DNS resolution anomalies.
The technical flaw stems from how rpc.mountd processes hostname resolution during mount operations. When a client connects with a hostname that produces different results between forward DNS lookups (A record resolution) and reverse DNS lookups (PTR record resolution), the daemon experiences a condition that leads to memory corruption or improper state handling. This inconsistency causes the service to crash and restart, effectively disrupting NFS operations for legitimate users. The vulnerability specifically exploits the difference between DNS resolution results, where the forward lookup returns one hostname while the reverse lookup returns another, creating an unexpected state within the mount daemon's internal processing logic.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability concerns. Organizations relying on NFS services for critical file sharing operations face potential downtime that can affect productivity and data availability. The denial of service occurs during the mount process when the rpc.mountd daemon encounters the inconsistent DNS resolution, leading to a complete service crash that requires manual intervention to restore. This vulnerability particularly affects environments where DNS configurations are complex or where clients connect through network address translation scenarios that can cause DNS resolution discrepancies. The attack requires minimal privileges and can be executed by any remote user capable of establishing an NFS mount connection, making it a significant concern for network administrators managing shared file systems.
Mitigation strategies for CVE-2004-0154 should focus on immediate patching of affected nfs-utils versions, specifically upgrading to version 1.0.6 or later where the vulnerability has been resolved. Network administrators should implement DNS consistency checks to ensure that forward and reverse DNS lookups return identical results for all hosts participating in NFS operations. Additionally, configuring rpc.mountd with stricter hostname validation parameters can help prevent malformed DNS responses from causing service crashes. The vulnerability aligns with CWE-129, which addresses improper handling of buffer content, and represents a classic example of how DNS resolution inconsistencies can be exploited for denial of service attacks. From an ATT&CK framework perspective, this vulnerability maps to the privilege escalation and denial of service tactics, as it allows attackers to disrupt services without requiring elevated privileges. Organizations should also consider implementing network segmentation to limit exposure and establish monitoring for unusual rpc.mountd behavior that might indicate exploitation attempts.