CVE-2026-64027 net: shaper: rework the VALID marking (again)
A race condition in the Linux kernel network shaper allows use-after-free, potentially leading to code execution or privilege escalation.
- 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-2026-64027?
CVE-2026-64027 is a high-severity vulnerability in Linux kernel, 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:
net: shaper: rework the VALID marking (again)
Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant.
The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU.
Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner.
Weakness: CWE-362
Which versions are affected by CVE-2026-64027?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64027?
Apply the vendor's patch.
Is CVE-2026-64027 being exploited?
There is no known exploitation of CVE-2026-64027 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64027, DEBIAN-CVE-2026-64027, GHSA-p8c9-j99c-x8w3, UBUNTU-CVE-2026-64027.