CVE-2008-4552 in nfs-utils
Summary
by MITRE
The good_client function in nfs-utils 1.0.9, and possibly other versions before 1.1.3, invokes the hosts_ctl function with the wrong order of arguments, which causes TCP Wrappers to ignore netgroups and allows remote attackers to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 08/28/2019
The vulnerability identified as CVE-2008-4552 affects the nfs-utils package version 1.0.9 and potentially other versions prior to 1.1.3, representing a critical flaw in network access control mechanisms. This issue specifically targets the good_client function within the nfs-utils implementation, which serves as a crucial component for managing client access to Network File System services. The flaw manifests through improper argument ordering when invoking the hosts_ctl function, a mechanism designed to enforce access control policies based on TCP Wrappers configuration files.
The technical root cause of this vulnerability lies in the incorrect parameter sequence passed to the hosts_ctl function, which fundamentally undermines the intended security controls. When the good_client function calls hosts_ctl with misordered arguments, the TCP Wrappers subsystem fails to properly evaluate netgroup entries within the configuration files. Netgroups represent collections of hosts or users that can be referenced collectively in access control rules, providing a powerful mechanism for managing complex access policies. The improper argument handling effectively bypasses these netgroup checks, allowing unauthorized access that would otherwise be blocked by well-defined security policies.
From an operational perspective, this vulnerability creates a significant security risk for NFS services that rely on TCP Wrappers for access control. Remote attackers can exploit this flaw to bypass intended restrictions without requiring authentication or authorization, potentially gaining access to sensitive file systems and data. The impact extends beyond simple unauthorized access, as it undermines the entire access control framework that administrators depend upon to secure their network services. This weakness particularly affects environments where netgroups are used extensively for managing access permissions across multiple hosts or user categories.
The vulnerability demonstrates a classic example of improper argument handling that can lead to security bypass conditions, aligning with CWE-457: Use of Uninitialized Variable and CWE-458: Incorrect Argument Ordering. From an attack perspective, this flaw maps to techniques described in the MITRE ATT&CK framework under TA0001 Initial Access and TA0003 Persistence, as attackers can leverage the bypass to establish unauthorized access to network resources. The vulnerability also relates to privilege escalation scenarios where attackers might use the bypass to gain higher-level access to system resources.
Mitigation strategies for this vulnerability require immediate patching of affected nfs-utils versions to 1.1.3 or later, where the argument ordering issue has been corrected. System administrators should also conduct comprehensive audits of their TCP Wrappers configurations to identify any potential bypass opportunities that may have existed prior to patching. Additional security measures include implementing network segmentation, using firewalls to restrict NFS service access, and monitoring for unauthorized access attempts. Organizations should also review their overall access control policies to ensure that multiple layers of security are maintained, as relying solely on TCP Wrappers becomes insufficient when such fundamental flaws exist in the implementation. The vulnerability highlights the critical importance of proper function parameter validation and the potential consequences of seemingly minor coding errors in security-sensitive applications.