CVE-2001-0822 in FPF Linux Kernel Module
Summary
by MITRE
FPF kernel module 1.0 allows a remote attacker to cause a denial of service via fragmented packets.
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Analysis
by VulDB Data Team • 04/10/2019
The vulnerability identified as CVE-2001-0822 affects the FPF kernel module version 1.0, representing a significant security flaw that enables remote attackers to execute denial of service attacks through the manipulation of network packets. This issue resides within the kernel space of operating systems that utilize the FPF module, creating a pathway for malicious actors to disrupt system availability without requiring elevated privileges. The vulnerability specifically targets the module's handling of fragmented network packets, which are commonly used in network communications to transmit large data segments across networks with varying maximum transmission unit sizes.
The technical flaw manifests when the FPF kernel module fails to properly process or validate fragmented packets, leading to potential system instability or complete system crash. This occurs because the module lacks adequate input validation mechanisms for handling packet fragmentation, which is a standard network protocol feature. When remote attackers craft malicious fragmented packets specifically designed to exploit this weakness, the kernel module processes these packets in a manner that causes system resources to become exhausted or triggers unexpected behavior in the kernel's packet handling routines. The vulnerability essentially creates a condition where legitimate network traffic can be disrupted through carefully constructed malicious fragments that exploit the module's inadequate error handling capabilities.
The operational impact of this vulnerability extends beyond simple service disruption, as it can potentially lead to complete system compromise or availability loss for network services that depend on the affected kernel module. Remote attackers can exploit this weakness from any location on the network without requiring authentication or specific system access, making it particularly dangerous in environments where network exposure is high. Systems running kernel versions that include the vulnerable FPF module are susceptible to sustained denial of service attacks that can render network services unavailable for extended periods. The attack vector is particularly concerning because it operates at the kernel level, meaning that successful exploitation can potentially lead to system crashes or require system reboots to restore normal operation.
Security practitioners should prioritize patching or updating systems that contain the vulnerable FPF kernel module version 1.0, as this vulnerability represents a straightforward exploit that requires minimal technical skill to execute. The mitigation strategy should include immediate deployment of vendor-supplied patches or updates that address the packet fragmentation handling logic within the FPF module. Organizations should also implement network segmentation and monitoring to detect unusual packet fragmentation patterns that might indicate exploitation attempts. From a defensive perspective, this vulnerability aligns with CWE-129, which addresses issues related to improper input validation, and represents a classic example of how kernel-level flaws can be exploited to achieve denial of service outcomes. The attack pattern corresponds to techniques found in the ATT&CK framework under the T1499.004 subtechnique for network denial of service, where adversaries leverage system weaknesses to disrupt network availability.
The broader implications of this vulnerability highlight the importance of proper kernel module validation and input sanitization in operating system security. It demonstrates how seemingly minor flaws in kernel components can have significant operational impacts, particularly when these components handle fundamental network protocols. Organizations should conduct comprehensive vulnerability assessments to identify all instances of the FPF module and ensure that proper security controls are in place to prevent exploitation. Regular security updates and kernel monitoring are essential practices to prevent similar vulnerabilities from being exploited in operational environments, as this flaw represents a clear example of how inadequate validation can lead to system instability and service disruption.