CVE-2026-63970 vsock/virtio: bind uarg before filling zerocopy skb
A use-after-free vulnerability in the Linux kernel's vsock/virtio driver allows attackers to potentially execute code or escalate privileges via crafted network packets.
- 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-2026-63970?
CVE-2026-63970 is a high-severity use after free 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:
vsock/virtio: bind uarg before filling zerocopy skb
virtio_transport_send_pkt_info() allocates or reuses the zerocopy uarg before entering the send loop, but virtio_transport_alloc_skb() still fills the skb before it inherits that uarg. When fixed-buffer vectored zerocopy hits MAX_SKB_FRAGS, io_sg_from_iter() may partially attach managed frags and return -EMSGSIZE. The rollback path call kfree_skb() to free an skb that carries SKBFL_MANAGED_FRAG_REFS but no uarg, so skb_release_data() falls through to ordinary frag unref.
Pass the uarg into virtio_transport_alloc_skb() and bind it immediately before virtio_transport_fill_skb(). This keeps control or no-payload skbs untouched while ensuring success and rollback share one lifetime rule.
Which versions are affected by CVE-2026-63970?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63970?
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-2026-63970 being exploited?
There is no known exploitation of CVE-2026-63970 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63970, DEBIAN-CVE-2026-63970, GHSA-mmvg-f8x9-hvr5, ROOT-OS-DEBIAN-13-CVE-2026-63970, UBUNTU-CVE-2026-63970.