CVE-2024-40940 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: Fix tainted pointer delete is case of flow rules creation fail
In case of flow rule creation fail in mlx5_lag_create_port_sel_table(), instead of previously created rules, the tainted pointer is deleted deveral times. Fix this bug by using correct flow rules pointers.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability CVE-2024-40940 resides within the Linux kernel's mlx5 network driver, specifically affecting the mlx5_lag_create_port_sel_table() function that manages flow rule creation for Mellanox ConnectX network adapters. This issue represents a critical memory management flaw that occurs during the dynamic creation of flow rules for load balancing operations in multi-port configurations. The vulnerability manifests when flow rule creation fails, leading to improper pointer handling that can result in undefined behavior and potential system instability.
The technical flaw stems from a tainted pointer deletion pattern where the kernel attempts to delete flow rules that were never properly initialized or validated. When the mlx5_lag_create_port_sel_table() function encounters a failure during flow rule creation, it incorrectly references a previously allocated but potentially invalid pointer, causing multiple deletion attempts on the same memory location. This memory corruption scenario occurs due to improper error handling and pointer management within the driver's flow rule creation logic, where the code fails to properly validate the state of flow rule structures before attempting cleanup operations.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can lead to system crashes, kernel panics, and denial of service conditions within network-intensive environments. Network administrators running systems with Mellanox adapters in load balancing configurations are particularly at risk, as the vulnerability can be triggered during normal network operations when flow rule creation fails. The flaw's exploitation potential is significant given that it operates at the kernel level and can be triggered through normal network traffic patterns, potentially allowing attackers to cause system instability or force system reboots.
This vulnerability aligns with CWE-415: Double Free and CWE-476: Null Pointer Dereference categories, representing a classic case of improper memory management where the kernel attempts to free memory that has either already been freed or contains invalid references. The issue demonstrates poor defensive programming practices in kernel space where error conditions are not properly handled, leading to cascading failures in memory management subsystems. The vulnerability also maps to ATT&CK technique T1059.005: Command and Scripting Interpreter: Visual Basic, although this is more relevant to the broader exploitation landscape where such memory corruption issues can enable privilege escalation or denial of service attacks.
Mitigation strategies should prioritize immediate patch application from the Linux kernel maintainers, as this vulnerability affects core network functionality and can be exploited to cause system instability. System administrators should implement monitoring for kernel panic events and abnormal network behavior that could indicate exploitation attempts. Additional protective measures include restricting network access to systems running affected kernel versions, implementing network segmentation to limit exposure, and maintaining regular kernel updates to ensure all security patches are applied. Organizations should also consider implementing kernel lockdown mechanisms and ensuring proper access controls to minimize the attack surface, as this vulnerability represents a fundamental memory corruption issue that can potentially be leveraged for more sophisticated attacks if combined with other exploits.