CVE-2025-39738: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability in the Linux kernel's BTRFS filesystem has been identified as CVE-2025-39738, discovered and disclosed on September 11, 2025. The issue affects the BTRFS filesystem's handling of partially dropped subvolumes during relocation operations (NVD).

The vulnerability manifests when balance operations trigger a transaction abort due to missing backref items for partially dropped subvolumes. The issue occurs specifically when attempting to handle tree blocks with bytenr 594526208, resulting in a BTRFS error with error code -117. The technical trace shows the error occurring in the btrfsrundelayed_refs function at ../fs/btrfs/extent-tree.c:2168 (NVD).

When triggered, the vulnerability causes transaction aborts in the BTRFS filesystem, potentially leading to filesystem operation failures. The issue specifically affects operations involving partially dropped subvolumes during relocation processes (NVD).

The issue has been addressed in the Linux kernel through a fix that prevents relocation of partially dropped subvolumes. Additionally, btrfs-progs will be enhanced to handle such cases. The root cause was previously addressed in upstream commit 8d488a8c7ba2 which fixed subvolume/snapshot deletion not being triggered on mount (NVD).