CVE-2021-47433 is a vulnerability identified in the Linux kernel's Btrfs filesystem implementation, specifically within the btrfs_replace_file_extents function. The issue arises from incorrect abort logic during error handling in the file extent replacement process. The vulnerability was discovered through error injection testing, which revealed a scenario where the filesystem could become corrupted due to a missing extent in the middle of a file. The root cause is a flawed conditional statement that determines whether the operation should abort upon encountering an error. The existing logic only aborts if the error code is not -EOPNOTSUPP and the call originated from the file clone code path. However, the preallocation code also uses this path and should trigger an abort on any error except -EOPNOTSUPP when called from the clone file code. This incorrect handling can lead to silent corruption of files, undermining data integrity. The vulnerability affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and was published on May 22, 2024. There are no known exploits in the wild, and no CVSS score has been assigned yet. The issue is significant because Btrfs is a widely used copy-on-write filesystem in Linux environments, often employed in enterprise and cloud infrastructure for its advanced features like snapshots and checksums. Improper handling of file extents can cause data loss or corruption, impacting system stability and reliability.

For European organizations, the impact of this vulnerability can be substantial, especially for those relying on Linux servers using the Btrfs filesystem for critical data storage and management. Data corruption within files can lead to loss of important information, disruption of services, and potential downtime. This is particularly critical for sectors such as finance, healthcare, government, and telecommunications, where data integrity and availability are paramount. The silent nature of the corruption means that affected organizations might not immediately detect the issue, potentially leading to prolonged data integrity problems and complicating forensic analysis. Additionally, organizations using Btrfs in cloud or virtualized environments may face cascading effects if corrupted files propagate through backups or snapshots. Although no active exploits are known, the vulnerability's presence in the kernel means that attackers with local access or the ability to trigger file extent replacements could exploit it to cause denial of service or data integrity attacks. This risk is heightened in multi-tenant environments common in European data centers.

To mitigate this vulnerability, European organizations should prioritize updating their Linux kernel to the patched version that corrects the abort logic in btrfs_replace_file_extents. Kernel updates should be tested in staging environments to ensure compatibility before deployment. Organizations should also audit their systems to identify any use of the Btrfs filesystem and assess the criticality of data stored on it. Implementing robust backup and recovery procedures is essential to recover from potential data corruption. Monitoring tools should be enhanced to detect filesystem anomalies or errors related to Btrfs operations. Additionally, restricting local access to trusted users and employing strict access controls can reduce the risk of exploitation. For environments where immediate patching is not feasible, consider temporarily migrating critical data to alternative filesystems or storage solutions until the patch is applied. Finally, educating system administrators about this vulnerability and its symptoms can facilitate early detection and response.