CVE-2026-64390 ksmbd: track the connection owning a byte-range lock
A use-after-free vulnerability in the Linux kernel's ksmbd module allows attackers to execute arbitrary code or cause a denial of service via SMB multichannel operations.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64390?
CVE-2026-64390 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: track the connection owning a byte-range lock
SMB2_LOCK adds each granted byte-range lock to both the file lock list and the lock list of the connection which handled the request. The final close and durable handle paths, however, remove the connection list entry while holding fp->conn->llist_lock.
With SMB3 multichannel, the connection handling the LOCK request can be different from the connection which opened the file. The entry can therefore be removed under a different spinlock from the one protecting the list it belongs to. A concurrent traversal can then access freed struct ksmbd_lock and struct file_lock objects.
Record the connection owning each lock's clist entry and hold a reference to it while the entry is linked. Use that connection and its llist_lock for unlock, rollback, close, and durable preserve. Durable reconnect assigns the new connection as the owner when publishing the locks again.
Which versions are affected by CVE-2026-64390?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64390?
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-2026-64390 being exploited?
There is no known exploitation of CVE-2026-64390 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64390, DEBIAN-CVE-2026-64390, GHSA-pgh2-g34p-4j6m, ROOT-OS-DEBIAN-12-CVE-2026-64390, ROOT-OS-DEBIAN-13-CVE-2026-64390, ROOT-OS-UBUNTU-2204-CVE-2026-64390 and 1 more.