# CVE-2026-89742

## Summary

- **CVE ID:** CVE-2026-89742
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 14, 2026

## 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.

## Affected Products

- Linux — Linux (e8de370188d098bb49483c287b44925957c3c9b6)
- Linux — Linux (4.6)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (5.10.270)
- Linux — Linux (5.15.221)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/9a9929ec875ff20922c90c96fd544ae8a2a61a8d)
- [CNA](https://git.kernel.org/stable/c/e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0)
- [CNA](https://git.kernel.org/stable/c/211c68d817a3d9dc14c0026a59da7cac30f8147e)
- [CNA](https://git.kernel.org/stable/c/5cbef379a94b161726c5f504598bf4791d45cedc)
- [CNA](https://git.kernel.org/stable/c/00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a)
- [CNA](https://git.kernel.org/stable/c/fc79c07cdcde02c5b17633d78777de6ac2c14b29)
- [CNA](https://git.kernel.org/stable/c/26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6)
- [CNA](https://git.kernel.org/stable/c/bd8881c24a9520f9c3d3e855d866197f63e471a7)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.16%
- **EPSS Percentile:** 5.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-19._