CVE-2026-89742 rapidio: mport_cdev: fix use-after-free in dma_req_free()
A use-after-free in the Linux kernel RapidIO mport driver allows local attackers to potentially execute code or escalate privileges via the character device interface.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89742?
CVE-2026-89742 is a high-severity use after free vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-89742?
How do I fix CVE-2026-89742?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89742 being exploited?
There is no known exploitation of CVE-2026-89742 in the wild and no public exploit code.
Sources
Also known as AZL-100718, BELL-CVE-2026-89742, DEBIAN-CVE-2026-89742, GHSA-hcj7-cp6w-gvx9, UBUNTU-CVE-2026-89742.