CVE-2026-89505 RDMA/uverbs: Guard legacy bundles without method_elm
A null pointer dereference in the Linux kernel RDMA subsystem allows local attackers to cause a denial of service via malformed provider input.
- 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-2026-89505?
CVE-2026-89505 is a 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:
RDMA/uverbs: Guard legacy bundles without method_elm
The legacy write() path dispatches through a uverbs_api_write_method, but the uverbs_attr_bundle passed to provider code does not have an ioctl method element. If malformed provider input causes the common uverbs validation code to emit an error message, uverbs_get_handler_fn() dereferences the uninitialized method_elm pointer.
Initialize method_elm explicitly for legacy bundles and make uverbs_get_handler_fn() return NULL when no ioctl method is present. The legacy dispatcher continues to use its local write method, while the ioctl path continues to use the registered ioctl handler.
Which versions are affected by CVE-2026-89505?
How do I fix CVE-2026-89505?
Apply the vendor's patch.
Is CVE-2026-89505 being exploited?
There is no known exploitation of CVE-2026-89505 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-89505, GHSA-6frh-mf5h-mgw9, UBUNTU-CVE-2026-89505.