CVE-2025-21797 is a high-severity vulnerability identified in the Linux kernel, specifically within the HID (Human Interface Device) driver for Corsair Void headsets. The root cause of the vulnerability is a missing call to cancel_delayed_work_sync() in the corsair_void_remove() function. This omission leads to a use-after-free condition, classified under CWE-416, where delayed work items related to headset status are not properly canceled before the associated memory is freed. Consequently, this can cause the kernel to access freed memory, potentially leading to memory corruption, system instability, or arbitrary code execution within kernel space. The vulnerability requires local access with low privileges (PR:L), does not require user interaction (UI:N), and has low attack complexity (AC:L). The attack vector is local (AV:L), meaning an attacker must have some form of local access to exploit it. The impact on confidentiality, integrity, and availability is rated high (C:H/I:H/A:H), indicating that successful exploitation could allow an attacker to gain elevated privileges, execute arbitrary code, and cause denial of service or system crashes. Although no known exploits are currently reported in the wild, the vulnerability's nature and severity make it a significant risk, especially in environments where untrusted users have local access to Linux systems. The vulnerability affects specific Linux kernel versions identified by commit hashes, implying that systems running these or similar kernel versions are vulnerable until patched. The fix involves adding the missing cancel_delayed_work_sync() call to ensure proper cleanup of delayed work items, preventing use-after-free conditions.

For European organizations, this vulnerability poses a substantial risk, particularly in sectors relying heavily on Linux-based infrastructure such as telecommunications, finance, government, and critical infrastructure. The high severity and potential for privilege escalation mean that attackers with local access could compromise sensitive data, disrupt services, or establish persistent footholds within networks. Organizations that allow multi-user access or use Linux systems in shared environments (e.g., development servers, cloud platforms, or virtualized environments) are especially at risk. The use-after-free could be exploited to execute arbitrary code in kernel mode, leading to full system compromise. This could result in data breaches, operational downtime, and damage to reputation. Additionally, the vulnerability could be leveraged as a stepping stone for lateral movement within networks. Given the widespread use of Linux in European enterprises and public sector organizations, the impact could be broad if not addressed promptly.

European organizations should prioritize applying the official Linux kernel patches that address CVE-2025-21797 as soon as they become available. In the interim, organizations should: 1) Restrict local access to Linux systems to trusted users only, minimizing the risk of exploitation by unprivileged users. 2) Implement strict access controls and monitoring on systems running vulnerable kernel versions, including auditing for unusual kernel-level activity. 3) Use kernel live patching solutions where feasible to apply fixes without requiring system reboots, reducing downtime. 4) Harden Linux systems by disabling or limiting the use of HID devices like Corsair Void headsets if not essential, or by isolating such devices in controlled environments. 5) Employ endpoint detection and response (EDR) tools capable of detecting anomalous kernel behavior indicative of exploitation attempts. 6) Educate system administrators and users about the risks of local privilege escalation vulnerabilities and enforce least privilege principles. 7) Maintain an up-to-date inventory of Linux kernel versions deployed across the organization to quickly identify and remediate vulnerable systems.