CVE-2024-56774 is a vulnerability identified in the Linux kernel's Btrfs filesystem implementation, specifically within the btrfs_search_slot() function. The issue arises when the extent tree root pointer is corrupted and becomes NULL, which can occur under certain conditions such as when the rescue=ibadroots kernel parameter is used. In this scenario, the btrfs_search_slot() function attempts to access the extent tree without verifying if the root pointer is valid, leading to a null pointer dereference (null-ptr-deref). This results in a kernel crash or system instability. The vulnerability was discovered by Syzbot, an automated kernel fuzzing tool, which generated a reproducer that triggers this fault. The root cause is the lack of a sanity check for the btrfs root pointer before its use in btrfs_search_slot(). The fix involves adding this sanity check to prevent dereferencing a NULL pointer. Although this vulnerability does not appear to have known exploits in the wild at the time of publication, it represents a potential denial-of-service (DoS) vector through kernel panic or system crash. The affected versions are specific Linux kernel commits identified by their hashes, indicating the vulnerability is present in certain development or stable branches prior to the patch. No CVSS score has been assigned yet, and the vulnerability does not require user interaction or authentication to be triggered, but it does require conditions that corrupt the extent tree root, which may limit exploitation scenarios.

For European organizations, the impact of CVE-2024-56774 primarily involves potential denial-of-service conditions on Linux systems using the Btrfs filesystem. Btrfs is increasingly adopted in enterprise and cloud environments for its advanced features like snapshots and checksumming. A null pointer dereference in the kernel can cause system crashes, leading to service interruptions, data unavailability, and potential operational disruptions. This can affect servers, storage appliances, and embedded devices running vulnerable Linux kernels with Btrfs enabled. While this vulnerability does not directly lead to privilege escalation or data corruption, the resulting instability could be exploited by attackers to disrupt critical services or cause downtime. In sectors such as finance, healthcare, and critical infrastructure prevalent in Europe, such disruptions could have significant operational and reputational consequences. Moreover, recovery from kernel crashes may require manual intervention, increasing operational costs. Since no known exploits exist yet, the immediate risk is moderate, but the vulnerability should be addressed promptly to prevent future exploitation, especially in environments where Btrfs is used extensively.

European organizations should take the following specific steps to mitigate CVE-2024-56774: 1) Identify all Linux systems using Btrfs filesystems, especially those running kernel versions corresponding to the affected commits. 2) Apply the latest Linux kernel patches or updates that include the fix adding the sanity check in btrfs_search_slot(). If vendor-specific distributions are used (e.g., Ubuntu, Debian, Red Hat), monitor their security advisories for backported patches. 3) In environments where immediate patching is not feasible, consider temporarily disabling Btrfs or migrating critical data to alternative filesystems such as ext4 or XFS to reduce exposure. 4) Implement robust monitoring for kernel panics and system crashes to detect potential exploitation attempts early. 5) Review and limit the use of kernel parameters like rescue=ibadroots unless necessary, as they may increase the risk of triggering this vulnerability. 6) Conduct thorough testing of kernel updates in staging environments to ensure stability before production deployment. 7) Maintain regular backups and disaster recovery plans to minimize downtime impact in case of crashes. These targeted actions go beyond generic advice by focusing on filesystem usage, kernel version management, and operational controls specific to this vulnerability.