CVE-2017-18218 in Linux
Summary
by MITRE
In drivers/net/ethernet/hisilicon/hns/hns_enet.c in the Linux kernel before 4.13, local users can cause a denial of service (use-after-free and BUG) or possibly have unspecified other impact by leveraging differences in skb handling between hns_nic_net_xmit_hw and hns_nic_net_xmit.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2017-18218 resides within the Linux kernel's networking driver subsystem, specifically in the Hisilicon HNS (HiSilicon Network Subsystem) driver implementation. This flaw manifests in the file drivers/net/ethernet/hisilicon/hns/hns_enet.c and affects kernel versions prior to 4.13. The issue stems from improper handling of socket buffer (skb) structures during network packet transmission operations, creating a dangerous condition that can be exploited by local malicious users to compromise system stability and potentially execute arbitrary code.
The technical root cause involves a use-after-free vulnerability that occurs when the hns_nic_net_xmit_hw and hns_nic_net_xmit functions handle socket buffers differently during network packet processing. These two transmission functions have distinct approaches to managing skb structures, leading to a scenario where a freed memory reference becomes accessible again before the kernel properly deallocates the memory. This discrepancy creates a race condition where the kernel may attempt to access memory that has already been freed, resulting in kernel crashes or unpredictable behavior. The vulnerability is classified as a use-after-free condition under CWE-416, which represents a critical memory safety issue that can lead to system instability and potential privilege escalation.
The operational impact of this vulnerability extends beyond simple denial of service conditions. Local attackers can leverage this flaw to trigger kernel BUG messages and system crashes, effectively causing a denial of service that disrupts network connectivity and potentially affects other system services. In more sophisticated exploitation scenarios, the unstable memory conditions created by the use-after-free could be manipulated to execute arbitrary code with kernel privileges, representing a significant security risk. The vulnerability affects systems using Hisilicon network hardware components and demonstrates the critical importance of proper memory management in kernel space drivers. Attackers with local access can exploit this weakness to compromise system integrity, making it particularly concerning for server environments where local user access is common.
Mitigation strategies for CVE-2017-18218 primarily involve upgrading to Linux kernel version 4.13 or later, where the memory handling inconsistencies between the two transmission functions have been resolved through proper synchronization and memory management. System administrators should also implement monitoring solutions to detect unusual kernel crashes or BUG messages that could indicate exploitation attempts. The fix addresses the underlying memory management issue by ensuring consistent skb handling across both transmission paths, eliminating the conditions that allowed the use-after-free to occur. Additionally, organizations should maintain comprehensive patch management processes to ensure all systems running affected kernel versions receive timely updates. The vulnerability highlights the importance of thorough testing of kernel drivers under various network load conditions and demonstrates how seemingly minor differences in code implementation can create critical security weaknesses that require immediate attention and remediation.