CVE-2024-49869 is a vulnerability identified in the Linux kernel's Btrfs filesystem implementation, specifically in the 'send' functionality which is used for sending incremental filesystem changes. The issue arises from incorrect buffer overflow detection related to the handling of the 'name_cache_entry' structure's variable length array 'name'. Initially, the 'name' array was annotated with __counted_by() to improve overflow detection, but this annotation did not account for the NUL string terminator, causing the fortified kernel to mistakenly detect a buffer overflow and trigger a kernel panic (splat). The root cause is that the length of the 'name' array should correspond to 'name_len' plus one byte for the NUL terminator, but the code treated it as just 'name_len', leading to false positives in overflow detection. The fix involved not storing the NUL terminator in the cache entry since it is unnecessary, marking the 'name' array with __nonstring, and replacing strcpy() with memcpy() to comply with kernel coding guidelines. This correction aligns the 'name_len' field with the actual size of the 'name' array and prevents erroneous overflow detection and kernel crashes. The vulnerability does not appear to be exploitable for privilege escalation or remote code execution directly, but it can cause denial of service (DoS) through kernel panics when Btrfs send operations are performed. The vulnerability affects Linux kernel versions starting from commit c0247d289e73 and is relevant to systems using Btrfs. No known exploits are reported in the wild as of the publication date, and no CVSS score has been assigned yet.

For European organizations, the primary impact of CVE-2024-49869 is the potential for denial of service due to kernel panics triggered by the Btrfs send operation. Organizations relying on Btrfs for storage, backup, or replication may experience unexpected system crashes, leading to service interruptions, data unavailability, and operational disruptions. This is particularly critical for enterprises using Btrfs in production environments such as data centers, cloud providers, and infrastructure hosting critical applications. While the vulnerability does not directly lead to data breaches or privilege escalation, the availability impact can affect business continuity and service level agreements. Additionally, kernel panics can complicate incident response and recovery efforts, increasing downtime. European organizations with strict uptime requirements or those operating critical infrastructure should prioritize patching to avoid disruption. The vulnerability also highlights the importance of kernel fortification and memory safety in filesystem code, which is a common attack surface in Linux-based systems.

To mitigate CVE-2024-49869, European organizations should: 1) Apply the official Linux kernel patches that fix the buffer overflow detection logic in the Btrfs send code. This involves updating to a kernel version that includes the fix from commit c0247d289e73 or later. 2) If immediate patching is not feasible, temporarily avoid using the Btrfs send functionality, especially in automated backup or replication workflows, to prevent triggering the kernel panic. 3) Monitor kernel logs for fortify_report warnings or splat messages related to strcpy buffer overflows in Btrfs operations as early indicators of attempted exploitation or accidental triggers. 4) Conduct thorough testing of kernel updates in staging environments before deployment to ensure stability and compatibility. 5) Maintain robust backup and recovery procedures to minimize impact from potential system crashes. 6) Consider using alternative filesystems for critical workloads if Btrfs usage is extensive and patching is delayed. 7) Engage with Linux distribution vendors for timely security updates and advisories related to this vulnerability.