CVE-2024-49884 is a use-after-free vulnerability identified and resolved in the Linux kernel's ext4 filesystem implementation, specifically within the ext4_split_extent_at() function. The vulnerability arises during the handling of extent splitting operations, where the kernel improperly manages memory paths related to extent trees. The flaw occurs when ext4_find_extent() is called to update the path structure, which may have already been freed under certain error conditions (-ENOMEM or -EIO). This leads to a use-after-free scenario where the kernel attempts to access or manipulate memory that has been deallocated, causing undefined behavior. The issue is triggered during write operations involving ext4_do_writepages(), which calls ext4_map_blocks() and subsequently ext4_ext_map_blocks(), eventually reaching ext4_split_extent_at(). The vulnerability is detected by Kernel Address Sanitizer (KASAN) as a slab-use-after-free error, indicating a read of freed memory. The root cause is improper handling of the extent path pointer after an error return from ext4_find_extent(), leading to dereferencing a stale pointer. The fix involves careful management of the path pointer, avoiding use-after-free by not using *ppath directly when EXT_DEBUG is defined and preventing unnecessary path updates. This vulnerability affects Linux kernel versions containing the specified commit hash dfe5080939ea4686b3414b5d970a9b26733c57a4, which corresponds to recent kernel versions around 6.9.0. The vulnerability does not currently have known exploits in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-49884 can be significant, especially for those relying heavily on Linux servers using the ext4 filesystem, which is the default filesystem for many Linux distributions widely deployed in enterprise environments. Exploitation of this vulnerability could lead to kernel crashes (denial of service) or potentially enable attackers to execute arbitrary code with kernel privileges if combined with other vulnerabilities or conditions, thereby compromising system confidentiality, integrity, and availability. This is particularly critical for data centers, cloud providers, and critical infrastructure operators in Europe that depend on Linux-based systems for hosting services, databases, and applications. The use-after-free flaw could be triggered by local users or processes with write access to ext4 filesystems, which may include containerized environments or virtual machines running on Linux hosts. Although remote exploitation is less likely without additional attack vectors, insider threats or compromised accounts could leverage this vulnerability to escalate privileges or disrupt operations. Given the widespread use of Linux in European governmental, financial, and industrial sectors, unpatched systems could face operational disruptions, data loss, or unauthorized access risks.

European organizations should prioritize updating their Linux kernel to the patched versions that include the fix for CVE-2024-49884. Specifically, they should: 1) Identify all systems running vulnerable Linux kernel versions, particularly those using ext4 filesystems. 2) Apply kernel updates from trusted Linux distribution vendors as soon as patches become available. 3) For environments where immediate patching is not feasible, consider temporarily restricting write operations to ext4 filesystems or isolating critical systems to limit exposure. 4) Enable and monitor kernel debugging and sanitization tools such as KASAN in test environments to detect similar memory corruption issues proactively. 5) Implement strict access controls and auditing on systems with ext4 filesystems to detect suspicious activities that might attempt to exploit this vulnerability. 6) Employ layered security controls such as SELinux or AppArmor to limit the impact of potential kernel exploits. 7) Regularly back up critical data and test recovery procedures to mitigate the impact of potential denial-of-service or data corruption incidents resulting from exploitation attempts.