CVE-2013-7441 in Network Block Device
Summary
by MITRE
The modern style negotiation in Network Block Device (nbd-server) 2.9.22 through 3.3 allows remote attackers to cause a denial of service (root process termination) by (1) closing the connection during negotiation or (2) specifying a name for a non-existent export.
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Analysis
by VulDB Data Team • 05/19/2022
The vulnerability identified as CVE-2013-7441 affects the Network Block Device server implementation in versions 2.9.22 through 3.3, representing a critical denial of service weakness that can result in complete system compromise. This issue manifests during the modern style negotiation phase of the nbd protocol where the server process fails to properly handle connection termination and export validation scenarios. The vulnerability stems from inadequate error handling mechanisms within the negotiation process, specifically when dealing with malformed connection states or invalid export requests. The flaw exists in the server's response to client disconnections during negotiation and improper validation of export names, creating opportunities for remote attackers to disrupt service availability.
The technical implementation of this vulnerability exploits the server's failure to properly validate connection states and export specifications during the modern style negotiation phase. When an attacker closes a connection abruptly during the negotiation process, or attempts to access a non-existent export by specifying an invalid name, the nbd-server process experiences a critical failure that results in immediate termination of the root process. This behavior represents a classic buffer overflow or improper state handling vulnerability that falls under the category of improper error handling as defined by CWE-704. The root process termination occurs because the server fails to implement proper exception handling or graceful degradation mechanisms when encountering unexpected connection states or invalid export requests.
Operationally, this vulnerability presents significant risk to systems relying on nbd-server for remote storage access, particularly in enterprise environments where uninterrupted service availability is critical. The impact extends beyond simple service disruption as the termination of the root process can lead to complete system compromise and potential data loss. Attackers can leverage this vulnerability to repeatedly cause service outages, effectively creating a persistent denial of service condition that can be difficult to detect and remediate. The vulnerability's remote nature means that attackers do not require local access or authentication credentials to exploit the issue, making it particularly dangerous in networked environments. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique of network denial of service, where adversaries leverage protocol weaknesses to disrupt availability.
The mitigation strategies for CVE-2013-7441 involve immediate patching of affected nbd-server versions to address the improper error handling in the modern style negotiation process. System administrators should implement connection timeout mechanisms and connection rate limiting to reduce the effectiveness of potential exploitation attempts. Additionally, monitoring should be implemented to detect unusual connection patterns or repeated termination events that may indicate exploitation attempts. Network segmentation and access control measures should be enforced to limit exposure of nbd-server instances to trusted networks only. The fix should include proper exception handling for connection closure events and validation of export names against a known, valid export list to prevent access to non-existent resources. Organizations should also consider implementing intrusion detection systems that can identify the specific patterns associated with this vulnerability to provide early warning of exploitation attempts.