CVE-2026-63812 f2fs: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node()
Incorrect handling of extent node destruction in the f2fs filesystem can lead to stale cached data and filesystem corruption errors.
- 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-2026-63812?
CVE-2026-63812 is a high-severity 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: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node()
When __destroy_extent_node() sets the inode flag FI_NO_EXTENT, it does not reset the length of the largest extent to 0 and update the inode folio. Since modifications to the extent tree are disallowed afterward, the cached largest extent may become stale. This can trigger the following error in xfstests generic/388:
F2FS-fs (dm-0): sanity_check_extent_cache: inode (ino=1761) extent info [220057, 57, 6] is incorrect, run fsck to fix
In the f2fs_drop_inode path, __destroy_extent_node() does not need to guarantee that et->node_cnt is 0, because concurrency with writeback is expected in this path, and writeback may update the extent cache.
This patch reverts commit ed78aeebef05 ("f2fs: fix node_cnt race between extent node destroy and writeback"), and remove the unnecessary zero check of et->node_cnt.
Which versions are affected by CVE-2026-63812?
How do I fix CVE-2026-63812?
Apply the vendor's patch.
Is CVE-2026-63812 being exploited?
There is no known exploitation of CVE-2026-63812 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63812, DEBIAN-CVE-2026-63812, GHSA-7w3g-6v3x-44mp, UBUNTU-CVE-2026-63812.