CVE-2025-40053 in Linux
Summary
by MITRE • 10/28/2025
In the Linux kernel, the following vulnerability has been resolved:
net: dlink: handle copy_thresh allocation failure
The driver did not handle failure of `netdev_alloc_skb_ip_align()`. If the allocation failed, dereferencing `skb->protocol` could lead to a NULL pointer dereference.
This patch tries to allocate `skb`. If the allocation fails, it falls back to the normal path.
Tested-on: D-Link DGE-550T Rev-A3
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Analysis
by VulDB Data Team • 05/20/2026
The vulnerability identified as CVE-2025-40053 resides within the Linux kernel's networking subsystem, specifically affecting the dlink network driver implementation. This issue represents a classic null pointer dereference vulnerability that can occur during network packet processing when memory allocation fails. The dlink driver, designed to support D-Link network hardware including the DGE-550T Rev-A3 model, fails to properly handle memory allocation failures during socket buffer creation, creating a potential crash condition that could be exploited by malicious actors. The vulnerability stems from inadequate error handling in the driver's packet processing logic where the system attempts to allocate memory for network packets without validating the allocation success before proceeding with subsequent operations.
The technical flaw manifests when the `netdev_alloc_skb_ip_align()` function fails to allocate memory for a socket buffer structure. This allocation function is responsible for creating network packet buffers with proper IP alignment, which is essential for network packet processing. When allocation fails, the function returns a NULL pointer, but the driver code continues execution without checking for this failure condition. Subsequently, the code attempts to dereference the `skb->protocol` field of what is actually a NULL pointer, leading to a kernel panic or system crash. This behavior directly violates the principles of defensive programming and proper error handling in kernel space operations where all memory allocation calls must be validated before use. The vulnerability falls under CWE-476, which specifically addresses null pointer dereference conditions in software development practices.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling denial of service attacks against network services that rely on the affected dlink driver. An attacker could exploit this vulnerability by triggering network traffic patterns that consistently cause memory allocation failures, leading to repeated system crashes and service disruption. In environments where network availability is critical, such as enterprise networks or telecommunications infrastructure, this vulnerability could result in significant operational downtime and service degradation. The vulnerability affects systems running Linux kernel versions that include the affected dlink driver code, particularly those using D-Link network hardware in server or networking equipment deployments where continuous network availability is essential. The potential for exploitation through network-based attacks makes this vulnerability particularly concerning in multi-tenant or cloud environments where network services are exposed to untrusted network traffic.
Mitigation strategies for CVE-2025-40053 should focus on applying the upstream patch that implements proper error handling for memory allocation failures. The recommended approach involves ensuring that all calls to `netdev_alloc_skb_ip_align()` are validated for success before proceeding with packet processing operations. System administrators should prioritize kernel updates that include the patched driver code, particularly for production systems running D-Link network hardware. Additionally, implementing network monitoring solutions that can detect anomalous packet processing patterns or system crash events can help identify potential exploitation attempts. The patch addresses this issue by implementing a fallback mechanism that gracefully handles allocation failures, allowing the driver to continue normal operation rather than crashing the kernel. Organizations should also consider implementing network segmentation and access controls to limit exposure of affected systems to untrusted network traffic, reducing the attack surface for potential exploitation. This vulnerability demonstrates the importance of comprehensive error handling in kernel drivers and aligns with ATT&CK technique T1499.004 for network denial of service attacks through kernel-level vulnerabilities.