CVE-2018-14641 in Linux
Summary
by MITRE
A security flaw was found in the ip_frag_reasm() function in net/ipv4/ip_fragment.c in the Linux kernel from 4.19-rc1 to 4.19-rc3 inclusive, which can cause a later system crash in ip_do_fragment(). With certain non-default, but non-rare, configuration of a victim host, an attacker can trigger this crash remotely, thus leading to a remote denial-of-service.
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Analysis
by VulDB Data Team • 05/17/2023
The vulnerability identified as CVE-2018-14641 represents a critical denial-of-service flaw within the Linux kernel's network stack implementation. This issue specifically affects kernel versions ranging from 4.19-rc1 through 4.19-rc3, where the ip_frag_reasm() function in the net/ipv4/ip_fragment.c file contains a memory management defect that can lead to system instability. The flaw operates at the kernel level and demonstrates how seemingly minor implementation details in network processing can result in catastrophic system failures.
The technical root cause of this vulnerability stems from improper handling of fragmented IP packets within the kernel's network reassembly logic. When the ip_frag_reasm() function processes incoming fragmented packets, it fails to properly validate or manage memory allocations during the reassembly process. This memory management error creates a condition where subsequent calls to ip_do_fragment() can trigger a kernel panic or system crash. The vulnerability is particularly concerning because it operates within the core network processing pathways that handle incoming packet traffic, making it accessible through normal network operations.
The operational impact of CVE-2018-14641 extends beyond simple service disruption, as it enables remote attackers to deliberately induce system crashes without requiring elevated privileges or specialized access. The vulnerability requires only that the victim system be configured with specific non-default networking parameters that are not uncommon in production environments. This configuration typically involves particular settings related to IP fragment handling and memory allocation policies that are sometimes implemented for performance optimization or specific network requirements. Attackers can exploit this by crafting malicious fragmented IP packets that trigger the flawed reassembly logic, causing the target system to become unresponsive and requiring manual intervention to restore normal operation.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates how improper memory handling can lead to system instability. From an ATT&CK perspective, this represents a denial-of-service attack technique that leverages kernel-level vulnerabilities to compromise system availability. The attack surface is particularly broad since any system running affected kernel versions and configured with the specific network parameters can be targeted. Organizations should consider implementing network segmentation and monitoring to detect unusual fragmentation patterns that might indicate exploitation attempts. The fix for this vulnerability required modifications to the kernel's IP fragment reassembly code to properly handle memory allocation and deallocation, ensuring that resources are correctly managed during packet processing operations.
This vulnerability highlights the importance of thorough testing and validation of kernel networking components, particularly those handling packet reassembly and memory management. The issue demonstrates how seemingly isolated kernel subsystems can create cascading failures when memory management is not properly handled, emphasizing the need for comprehensive security testing of core system components. The remote exploitability of this vulnerability makes it particularly dangerous in environments where systems are exposed to untrusted network traffic, as it can be used to systematically disrupt network services without requiring authentication or privileged access.