CVE-2011-2500 in nfs-utils
Summary
by MITRE
The host_reliable_addrinfo function in support/export/hostname.c in nfs-utils before 1.2.4 does not properly use DNS to verify access to NFS exports, which allows remote attackers to mount filesystems by establishing crafted DNS A and PTR records.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/01/2022
The vulnerability identified as CVE-2011-2500 resides within the nfs-utils package version 1.2.3 and earlier, specifically in the host_reliable_addrinfo function located in support/export/hostname.c. This flaw represents a significant security weakness in the Network File System implementation that affects how the system validates network addresses during NFS export operations. The issue stems from improper DNS verification mechanisms that fail to adequately validate access to NFS exports through the DNS resolution process.
The technical implementation flaw occurs when the host_reliable_addrinfo function processes DNS lookups for hostname resolution. Instead of properly validating that the resolved addresses actually correspond to legitimate network endpoints capable of serving NFS exports, the function accepts DNS records without sufficient verification. This allows attackers to manipulate DNS responses through crafted A and PTR records, effectively bypassing the intended access controls. The vulnerability specifically affects the DNS resolution workflow where the system relies on DNS lookups to determine host accessibility for NFS export mounting operations.
Operational impact of this vulnerability is substantial as it enables remote attackers to mount filesystems they should not have access to simply by controlling DNS records within their scope. An attacker can create malicious A records pointing to their own systems or manipulate existing DNS entries to redirect NFS mount requests to unauthorized endpoints. This creates a privilege escalation scenario where unauthorized users can gain access to NFS exports that should be restricted to legitimate users. The vulnerability essentially allows for arbitrary NFS mount operations through DNS manipulation, undermining the fundamental security model of NFS access control.
The security implications extend beyond simple unauthorized access, as this vulnerability can be exploited to bypass network segmentation controls and gain access to sensitive data stored on NFS shares. Attackers can leverage this weakness to perform reconnaissance and potentially escalate privileges within network environments where NFS is used for file sharing. The vulnerability aligns with CWE-20 Improper Input Validation and can be mapped to ATT&CK technique T1071.004 Application Layer Protocol: DNS, as it exploits DNS resolution mechanisms for malicious purposes. Organizations using nfs-utils versions prior to 1.2.4 face significant risk of unauthorized data access and potential data exfiltration through this vulnerability.
Mitigation strategies include upgrading to nfs-utils version 1.2.4 or later, where the DNS verification logic has been properly implemented to prevent the exploitation of this vulnerability. Network administrators should also implement DNS security measures such as DNSSEC to prevent DNS spoofing attacks that could exploit this weakness. Additional defensive measures include monitoring DNS queries for unusual patterns and implementing proper access controls on NFS export configurations. The fix in the updated version ensures that DNS resolution results are properly validated before being accepted for NFS export operations, preventing attackers from manipulating DNS records to gain unauthorized access to network file systems.