CVE-2026-23465 btrfs: log new dentries when logging parent dir of a conflicting inode

Medium 5.5 Published 3 Apr 2026 Updated 11 May 2026

A logic error in the btrfs filesystem causes new directory entries to be lost after a power failure if specific fsync operations are performed.

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-2026-23465?

CVE-2026-23465 is a medium-severity denial of service vulnerability in Linux kernel, published on 3 Apr 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:

btrfs: log new dentries when logging parent dir of a conflicting inode

If we log the parent directory of a conflicting inode, we are not logging the new dentries of the directory, so when we finish we have the parent directory's inode marked as logged but we did not log its new dentries. As a consequence if the parent directory is explicitly fsynced later and it does not have any new changes since we logged it, the fsync is a no-op and after a power failure the new dentries are missing.

Example scenario:

$ mkdir foo

$ sync

$rmdir foo

$ mkdir dir1 $ mkdir dir2

# A file with the same name and parent as the directory we just deleted # and was persisted in a past transaction. So the deleted directory's # inode is a conflicting inode of this new file's inode. $ touch foo

$ ln foo dir2/link

# The fsync on dir2 will log the parent directory (".") because the # conflicting inode (deleted directory) does not exists anymore, but it # it does not log its new dentries (dir1). $ xfs_io -c "fsync" dir2

# This fsync on the parent directory is no-op, since the previous fsync # logged it (but without logging its new dentries). $ xfs_io -c "fsync" .

# After log replay dir1 is missing.

Fix this by ensuring we log new dir dentries whenever we log the parent directory of a no longer existing conflicting inode.

A test case for fstests will follow soon.

Which versions are affected by CVE-2026-23465?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-23465?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-23465 being exploited?

There is no known exploitation of CVE-2026-23465 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2026-23465, DEBIAN-CVE-2026-23465, GHSA-wm46-26gp-9px3, ROOT-OS-DEBIAN-11-CVE-2026-23465, ROOT-OS-DEBIAN-12-CVE-2026-23465, ROOT-OS-UBUNTU-2204-CVE-2026-23465 and 2 more.