CVE-2022-49409 is a vulnerability identified in the Linux kernel's ext4 filesystem implementation, specifically related to the handling of extents within the ext4 extents status tree. The flaw arises from improper validation of extent entries in the ext4_valid_extent_entries function. Extents are data structures used by ext4 to efficiently map file data blocks. The vulnerability occurs because the check for overlapping extents does not correctly apply to the second and subsequent extents due to a logic error where the 'prev' variable is zeroed, causing the function to skip necessary validation. This leads to a situation where extents can overlap or be out of order without triggering an error. When the kernel subsequently processes these malformed extents in the __es_tree_search function, it triggers a BUG_ON condition, which is a kernel panic assertion designed to catch critical errors. This results in a system crash (kernel panic), causing a denial of service (DoS). The issue manifests during filesystem mount operations or quota enabling, as the ext4_fill_super function and related quota functions traverse and validate extents. The root cause is a missing check that the logical block number (lblock) of the first extent is not less than zero and that subsequent extents start after the previous extent ends. The fix involves adding these boundary checks to prevent overlapping or misordered extents. This vulnerability affects Linux kernel versions containing the specified commits and is particularly relevant to systems using ext4, which is the default filesystem in many Linux distributions. There are no known exploits in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2022-49409 can be significant, especially for those relying heavily on Linux servers with ext4 filesystems. The vulnerability can cause kernel panics leading to system crashes and denial of service, which can disrupt critical services, data processing, and operations. This is particularly concerning for infrastructure providers, cloud services, web hosting, and enterprises running production workloads on Linux. The DoS condition could be triggered remotely if an attacker can manipulate filesystem metadata or locally if malicious or corrupted filesystems are mounted. Although no direct code execution or privilege escalation is indicated, the availability impact alone can cause operational downtime, data unavailability, and potential cascading failures in distributed systems. Additionally, systems that enable quotas on ext4 filesystems are also at risk during quota operations. The lack of known exploits reduces immediate risk, but the vulnerability's presence in widely deployed Linux kernels means that attackers could develop exploits in the future. European organizations with compliance requirements for uptime and data integrity must prioritize remediation to avoid service interruptions and potential reputational damage.

To mitigate CVE-2022-49409, organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from trusted Linux distribution vendors or kernel maintainers. 2) For environments where immediate patching is not feasible, avoid mounting untrusted or potentially corrupted ext4 filesystems and disable quota features on ext4 filesystems if not required, as the vulnerability is triggered during quota enabling. 3) Implement filesystem integrity monitoring and regular backups to detect and recover from filesystem corruption or crashes. 4) Use kernel crash dump and monitoring tools to detect and analyze kernel panics related to ext4, enabling faster incident response. 5) Limit access to systems that can mount filesystems or enable quotas to trusted administrators only, reducing the risk of malicious manipulation. 6) In virtualized or containerized environments, isolate workloads and limit exposure of ext4 mounts to reduce attack surface. 7) Monitor security advisories from Linux distributions and maintain an up-to-date inventory of kernel versions deployed across infrastructure to prioritize patching efforts.