CVE-2023-52855 is a concurrency-related vulnerability in the Linux kernel's USB driver subsystem, specifically within the dwc2 (DesignWare Core USB 2.0) host controller driver. The flaw arises from improper synchronization when handling USB Request Blocks (URBs) in the functions _dwc2_hcd_urb_enqueue() and _dwc2_hcd_urb_dequeue(). In _dwc2_hcd_urb_enqueue(), the pointer urb->hcpriv is set to NULL without holding the required spinlock (hsotg->lock). Concurrently, _dwc2_hcd_urb_dequeue() acquires the lock and checks urb->hcpriv for NULL before using it. Due to the race condition, the NULL check in dequeue can occur before enqueue sets urb->hcpriv to NULL, leading to a scenario where dwc2_hcd_urb_dequeue() uses a NULL pointer, causing a NULL pointer dereference and subsequent kernel crash (denial of service). This vulnerability was identified via static analysis focusing on locking API usage and concurrency bugs. The fix involves ensuring urb->hcpriv is set to NULL while holding the hsotg->lock, preventing the race condition. Although no runtime testing was performed due to lack of hardware, the patch logically resolves the issue. The vulnerability affects Linux kernel versions around commit 33ad261aa62be02f0cedeb4d5735cc726de84a3f, corresponding to Linux 6.5. The CVSS 3.1 score is 5.5 (medium severity), reflecting a local attack vector with low complexity, requiring privileges but no user interaction, and causing availability impact only (kernel crash). No known exploits are reported in the wild at this time.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions with the dwc2 USB host controller driver enabled. The impact is a potential denial of service via kernel crash caused by a NULL pointer dereference. This can disrupt critical services, especially in environments relying on Linux-based infrastructure such as servers, embedded devices, or network appliances using USB connectivity. While the attack vector is local and requires some privileges, insider threats or compromised accounts could exploit this flaw to cause system instability or outages. In sectors like manufacturing, telecommunications, or critical infrastructure where Linux-based embedded systems are common, this could lead to operational disruptions. However, the vulnerability does not expose confidentiality or integrity risks directly, limiting its impact to availability. Given the medium severity and lack of known exploits, the immediate threat level is moderate but should not be ignored, especially in high-availability environments.

European organizations should prioritize updating their Linux kernels to versions where this vulnerability is patched, specifically applying the fix that ensures urb->hcpriv is set to NULL under the hsotg->lock. For environments where immediate patching is not feasible, mitigating controls include restricting local access to trusted users only, minimizing the number of privileged accounts, and monitoring kernel logs for unusual USB driver errors or crashes. Additionally, organizations should audit their use of USB devices and consider disabling unused USB host controllers or ports to reduce attack surface. For embedded systems or appliances with limited update capabilities, vendors should be contacted for firmware or kernel updates incorporating this fix. Implementing kernel lockdown features and employing security modules like SELinux or AppArmor can further reduce risk by limiting the ability of local users to trigger this vulnerability. Finally, maintaining robust incident response plans to quickly recover from potential denial of service events is recommended.