CVE-2026-63816 f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode
A use-after-free vulnerability in the Linux kernel's f2fs atomic file handling allows attackers to cause a system crash or potentially execute arbitrary code.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63816?
CVE-2026-63816 is a high-severity use after free vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode
- ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink - f2fs_gc - gc_data_segment - ra_data_block(cow_inode) - mapping = F2FS_I(inode)->atomic_inode->i_mapping : f2fs_is_cow_file(cow_inode) is true - f2fs_evict_inode(atomic_inode) - clear_inode_flag(fi->cow_inode, FI_COW_FILE) - F2FS_I(fi->cow_inode)->atomic_inode = NULL ... - truncate_inode_pages_final(atomic_inode) - f2fs_grab_cache_folio(mapping) : create folio in atomic_inode->mapping - clear_inode(atomic_inode) - BUG_ON(atomic_inode->i_data.nrpages)
We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue.
Which versions are affected by CVE-2026-63816?
How do I fix CVE-2026-63816?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-63816 being exploited?
There is no known exploitation of CVE-2026-63816 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63816, DEBIAN-CVE-2026-63816, GHSA-gp48-qw68-qgg5, ROOT-OS-DEBIAN-12-CVE-2026-63816, UBUNTU-CVE-2026-63816.