Look up another CVE · open CVE-2026-89742 in the interactive tracker
CVE-2026-89742
rapidio: mport_cdev: fix use-after-free in dma_req_free()
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/rapidio. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-89742 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/rapidio/devices/rio_mport_cdev.c
- What this is
- RAPIDIO SUBSYSTEMMAINTAINERS section matched on drivers/rapidio/ · Maintained
- Kernel module
- none to look for. The file would have gone into rio_mport_cdev, and Debian does not compile it into that module, so finding rio_mport_cdev in lsmod would say nothing about this CVE.
Check it on the machine
grep -wE 'CONFIG_RAPIDIO|CONFIG_RAPIDIO_MPORT_CDEV' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switches
- CONFIG_RAPIDIO, CONFIG_RAPIDIO_MPORT_CDEV
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/rapidio
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.6 | 5.10.270 | 00c5ed913b0d |
| 4.6 | 5.15.221 | fc79c07cdcde |
| 4.6 | 6.1.188 | 26ccfe7d69e2 |
| 4.6 | 6.6.157 | bd8881c24a95 |
| 4.6 | 6.12.109 | 9a9929ec875f |
| 4.6 | 6.18.50 | e6e925cc1f80 |
| 4.6 | 7.2.4 | 211c68d817a3 |
| 4.6 | 7.3 | 5cbef379a94b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The use-after-free is reached only through local ioctls on /dev/rio_mportN (RIO_ALLOC_DMA, RIO_TRANSFER with a kernel DMA handle, RIO_FREE_DMA, then close or RIO_WAIT_FOR_ASYNC). RapidIO is a board-level fabric, and this dma_req_free() path is not driven by received packets.
- AC:LAttack complexity, low
- An attacker who can open the mport node deterministically allocates a DMA mapping, submits an async RIO_TRANSFER that takes a kref on it, drops the owner ref with RIO_FREE_DMA, then frees the request so dma_req_free() performs the last kref_put(); no condition outside the attacker’s control is required.
- PR:LPrivileges required, low
- mport_cdev_open() and the DMA ioctls perform no capable() checks; access is gated only by /dev/rio_mportN permissions, and RapidIO deployments commonly give fabric-management daemons group access to that node, so an unprivileged local user with the device can drive the bug.
- UI:NUser interaction, none
- Exploitation is entirely self-driven via the attacker’s own open/ioctl/close sequence on the mport character device; no separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The freed rio_mport_mapping and the subsequent mutex unlock occur in kernel heap within the host OS authority; this is a standard kernel use-after-free and does not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- dma_req_free() dereferences req->map after mport_release_mapping() has kfree’d that kmalloc object; reclaiming the slab lets an attacker control map->md and read through the dangling pointer, a classic use-after-free disclosure primitive.
- I:HIntegrity impact, high
- Unlocking buf_mutex via a reclaimed map->md causes mutex_unlock() on an attacker-chosen address (fake-mutex wait_list write), so the use-after-free is exploitable for arbitrary kernel write and control-flow hijack.
- A:HAvailability impact, high
- Use-after-free of rio_mport_mapping during mutex_unlock() oopses or panics under slab poisoning or init_on_free, and targeting a fake md leaves the real buf_mutex locked, deadlocking mapping paths and crashing or hanging the kernel.