CVE-2024-43845 is a vulnerability identified in the Linux kernel's implementation of the Universal Disk Format (UDF) filesystem, specifically within the udf_rename() function. The issue arises from a bogus checksum computation performed on the '..' directory entry of a moved directory. The root cause is that the checksum function udf_update_tag() is called with an on-stack structure (diriter.fi) that only contains a partial file identifier descriptor (struct fileIdentDesc) without the full fields (impUse or name) required for a correct checksum calculation. Consequently, the checksum function reads uninitialized stack memory beyond the structure's end, leading to an incorrect checksum calculation. However, this incorrect checksum is later overwritten by udf_fiiter_write_fi(), which recalculates the checksum correctly from on-disk buffers. Therefore, the vulnerability does not lead to persistent corruption or data integrity issues but represents a flaw in the kernel code that could potentially be exploited to read uninitialized kernel stack memory. This could theoretically lead to information disclosure if an attacker can trigger the udf_rename() operation and access the resulting data. The patch involves removing the bogus checksum calculation to prevent reading uninitialized memory. There are no known exploits in the wild, and no CVSS score has been assigned yet. The vulnerability was published on August 17, 2024.

For European organizations, the impact of CVE-2024-43845 is primarily related to potential information disclosure through uninitialized kernel memory access. While the vulnerability does not cause data corruption or system instability, the ability to read uninitialized kernel stack memory could allow attackers to glean sensitive information residing temporarily in memory, such as cryptographic keys, passwords, or other sensitive data. This risk is particularly relevant for organizations running Linux systems with UDF filesystems, which are commonly used for optical media like DVDs and some removable storage devices. Sectors with high security requirements, such as government, finance, and critical infrastructure in Europe, could be concerned about any leakage of sensitive information. However, since exploitation requires triggering a rename operation on UDF filesystems and no known exploits exist, the immediate risk is moderate. The vulnerability does not affect system availability or integrity directly, but the confidentiality impact warrants attention.

European organizations should prioritize applying the official Linux kernel patch that removes the bogus checksum calculation in udf_rename(). Until patches are deployed, organizations can mitigate risk by limiting or monitoring the use of UDF filesystems, especially restricting rename operations on such filesystems to trusted users only. Employing kernel security modules (e.g., SELinux, AppArmor) to restrict filesystem operations and monitoring kernel logs for unusual rename activity on UDF filesystems can help detect exploitation attempts. Additionally, organizations should ensure that all Linux systems are regularly updated with the latest kernel security patches and consider disabling or unmounting UDF filesystems if not required. For environments where UDF usage is necessary, implementing strict access controls and auditing can reduce the attack surface. Finally, educating system administrators about this vulnerability and encouraging prompt patch management will help mitigate potential risks.