CVE-2024-49960 is a vulnerability identified in the Linux kernel's ext4 filesystem implementation. The issue arises from improper handling of a timer object (s_err_report) during a failed mount operation. Specifically, when mounting an ext4 filesystem fails, the kernel executes a cleanup routine (failed_mount3) that calls ext4_stop_mmpd, which leads to a read I/O failure. This failure triggers ext4_handle_error, which inadvertently re-arms the s_err_report timer. However, the timer is still active when the kernel attempts to free the superblock information structure (sbi) via kfree(sbi), resulting in a use-after-free condition on the timer object. This use-after-free bug can cause kernel instability or crashes, potentially leading to denial of service (DoS) conditions. The root cause is that the del_timer_sync function, which is supposed to cancel the timer safely, is not called at the correct point in the failure path. The fix involves ensuring that the s_err_report timer is properly canceled after ext4_stop_mmpd is called, preventing the timer from being active when the associated memory is freed. This vulnerability was discovered by Syzbot, an automated kernel fuzzing system, and affects multiple Linux kernel versions as indicated by the commit hashes. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet. The vulnerability affects the ext4 filesystem, which is widely used in Linux environments for local storage and embedded systems.

For European organizations, this vulnerability poses a risk primarily to systems running Linux with ext4 filesystems, which is common in servers, desktops, and embedded devices. Exploitation could lead to kernel crashes and system instability, resulting in denial of service. This can disrupt business operations, especially for critical infrastructure, cloud providers, and enterprises relying on Linux-based servers. While the vulnerability does not directly expose data confidentiality or integrity issues, the resulting DoS could impact availability of services. Organizations running containerized workloads or virtualized environments on Linux hosts with ext4 may also experience cascading effects if hosts become unstable. The absence of known exploits reduces immediate risk, but the vulnerability’s presence in the kernel means that attackers with local access or the ability to trigger mount failures could exploit it. European organizations with strict uptime requirements or those in sectors like finance, healthcare, and telecommunications should prioritize patching to avoid service disruptions.

1. Apply the official Linux kernel patches that address CVE-2024-49960 as soon as they become available from trusted sources or Linux distribution vendors. 2. For organizations using custom or long-term support kernels, backport the fix to maintain stability. 3. Monitor system logs for ext4 mount failures or unusual kernel timer activity that could indicate attempts to trigger this vulnerability. 4. Limit local user access and restrict the ability to mount filesystems to trusted administrators to reduce exploitation risk. 5. Employ kernel hardening techniques such as kernel lockdown modes and seccomp filters to limit attack surface. 6. Regularly update and audit Linux kernel versions and filesystem drivers to ensure timely application of security fixes. 7. In environments where immediate patching is not feasible, consider isolating vulnerable systems or using alternative filesystems temporarily to mitigate risk.