CVE-2000-0344 in Linux
Summary
by MITRE
The knfsd NFS server in Linux kernel 2.2.x allows remote attackers to cause a denial of service via a negative size value.
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Analysis
by VulDB Data Team • 10/16/2025
The CVE-2000-0344 vulnerability represents a critical denial of service flaw within the kernel-based network file system implementation of linux version 2.2.x. This vulnerability specifically affects the knfsd component which serves as the kernel-level nfs server daemon responsible for handling network file system requests from remote clients. The flaw arises from insufficient input validation mechanisms within the kernel's nfs server implementation, where negative size values are not properly sanitized before processing. When a remote attacker sends a malformed nfs request containing a negative size parameter, the kernel's nfs server fails to properly handle this invalid data structure, leading to system instability and eventual service disruption. This vulnerability operates at the kernel level and represents a classic buffer overflow or input validation issue that can be exploited without requiring authentication or special privileges. The impact extends beyond simple service interruption as the flaw can potentially cause the entire system to crash or become unresponsive, affecting all network services that rely on the kernel's nfs implementation.
The technical nature of this vulnerability aligns with CWE-129, which addresses improper validation of array indices and buffer bounds, and more specifically relates to CWE-126, which covers buffer over-read conditions. The flaw demonstrates a fundamental lack of proper input validation within the kernel's nfs server code where the system fails to validate that file size parameters fall within acceptable positive ranges. From an operational perspective, this vulnerability creates a significant risk for networked systems that rely on nfs services, as attackers can trigger system instability through simple network requests. The attack vector requires only network connectivity to the affected system and does not necessitate any authentication credentials or privileged access. This makes the vulnerability particularly dangerous as it can be exploited by anyone with network access to the target system, potentially allowing for widespread disruption of network services. The vulnerability affects systems running linux kernel versions 2.2.x where the knfsd module is enabled and actively serving nfs requests.
The operational impact of CVE-2000-0344 extends beyond immediate denial of service conditions to encompass broader system reliability concerns and potential data integrity issues. When exploited, the vulnerability can cause the kernel to enter an unstable state where system resources become unavailable or corrupted, potentially leading to complete system crashes that require manual rebooting. Organizations relying on nfs services for file sharing, backup operations, or distributed computing environments face significant operational risks from this vulnerability. The attack can be executed through standard network protocols and does not require specialized tools or extensive knowledge of system internals. From an attacker's perspective, this represents a low-effort, high-impact method of service disruption that can be automated and scaled across multiple targets. The vulnerability's exploitation aligns with tactics described in the mitre att&ck framework under the service disruption category, specifically targeting availability objectives within the attack lifecycle. System administrators must consider the broader implications of this vulnerability on network infrastructure reliability, as even a single compromised nfs server can affect multiple dependent services and applications across the network.
Mitigation strategies for CVE-2000-0344 primarily focus on immediate system updates and configuration changes to prevent exploitation. The most effective approach involves upgrading to linux kernel versions 2.2.16 or later where the vulnerability has been patched through proper input validation mechanisms. Organizations should implement network segmentation and access controls to limit exposure of nfs services to only trusted networks and hosts. Additional defensive measures include monitoring network traffic for suspicious nfs requests containing negative size parameters and implementing intrusion detection systems that can identify exploitation attempts. System administrators should also consider disabling nfs services when not required or implementing proper firewall rules to restrict nfs traffic to authorized endpoints. The patch for this vulnerability demonstrates the importance of proper input validation in kernel space code and highlights the need for comprehensive security testing of system components. Organizations should conduct regular vulnerability assessments to identify similar issues in other kernel modules and network services, as this vulnerability represents a pattern of insufficient input validation that can affect various system components. The incident underscores the critical nature of maintaining up-to-date system software and the potential for seemingly minor input validation flaws to result in significant system stability issues.