CVE-2025-40053

Vulnerability

Description

CVE-2025-40053 is a NULL pointer dereference vulnerability in the Linux kernel's D-Link (dlink) network driver. The driver calls netdev_alloc_skb_ip_align() to allocate a socket buffer (skb) but does not check whether the allocation succeeds. If the allocation fails, the code proceeds to dereference skb->protocol, leading to a NULL pointer dereference and a kernel crash [1][2][3].

Exploitation

An attacker with local access or the ability to trigger network activity on a D-Link DGE-550T (Rev-A3) interface could cause memory pressure conditions that make the SKB allocation fail. Because the driver lacks a proper error-handling path, subsequent access to the SKB's protocol field results in a NULL pointer dereference. No prior authentication is required to trigger the vulnerable code path when network traffic is processed [1][2][3].

Impact

Successful exploitation results in a denial-of-service (DoS) condition through a kernel crash. The issue may also be exploitable for privilege escalation or other arbitrary effects if an attacker can control the state of the allocation failure and the subsequent crash, though the primary impact is system availability loss [1][2][3].

Mitigation

The Linux kernel maintainers have fixed the issue by adding a fallback path when the SKB allocation fails, ensuring the driver does not dereference a NULL pointer. Users should apply the stable kernel updates containing the fix. No workaround is no workaround; the vulnerability is patched, and affected systems should update to the latest kernel version [1][2][3].