CVE-2026-98035 bpf: Cancel special fields when recycling rhtab elements
A race condition in Linux kernel BPF hash map recycling allows unsafe field release in NMI context, potentially leading to privilege escalation or denial of service.
- 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-2026-98035?
CVE-2026-98035 is a vulnerability in Linux, published on 25 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:
bpf: Cancel special fields when recycling rhtab elements
rhtab_map_update_existing() and rhtab_delete_elem() call bpf_obj_free_fields() when replacing or deleting a value. These map operations can run from BPF programs in NMI context, where releasing a referenced kptr or another complex field is not generally safe.
Array and hash maps avoid that problem by cancelling only the asynchronous fields which can be stopped safely in the caller context. Other ownership state remains attached to the allocation until its memory allocator destructor performs the final cleanup.
Use bpf_obj_cancel_fields() for the corresponding rhtab paths as well. This cancels timers, workqueues, and task work while allowing rhtab_mem_dtor() to release referenced kptrs when the allocation is eventually destroyed.
[ kkd: Rebased, used direct helper calls, and rewrote the commit log ]
Which versions are affected by CVE-2026-98035?
How do I fix CVE-2026-98035?
Apply the vendor's patch.
Is CVE-2026-98035 being exploited?
There is no known exploitation of CVE-2026-98035 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98035, GHSA-xmmm-c56c-hjqv, UBUNTU-CVE-2026-98035.