CVE-2026-98039 bpf: Require MEM_PERCPU for percpu kptr stores
A flaw in the Linux kernel BPF subsystem allows arbitrary kernel read/write and potential privilege escalation by bypassing per-CPU pointer type checks.
- 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-2026-98039?
CVE-2026-98039 is a memory corruption 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: Require MEM_PERCPU for percpu kptr stores
map_kptr_match_type() treats perm_flags as the set of register type flags that a kptr field permits. Adding MEM_PERCPU to that set for BPF_KPTR_PERCPU does not require the source register to carry it, however. The subset test consequently accepts both a plain bpf_obj_new() allocation and a referenced kernel pointer into a __percpu_kptr map field.
Loads from the field are always marked MEM_PERCPU. Consumers then treat the stored value as the cookie returned by bpf_percpu_obj_new(): per-CPU pointer helpers relocate it, and map teardown selects the per-CPU free path. A plain allocation can therefore provide an arbitrary kernel read/write, while a kernel pointer can be relocated into an invalid address or sent through a missing destructor.
Require the source MEM_PERCPU flag to match the destination field kind. This preserves valid bpf_percpu_obj_new() stores and rejects both the program-BTF and kernel-BTF variants.
Which versions are affected by CVE-2026-98039?
How do I fix CVE-2026-98039?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-98039 being exploited?
There is no known exploitation of CVE-2026-98039 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98039, DEBIAN-CVE-2026-98039, GHSA-hqcj-5pcp-63q5, UBUNTU-CVE-2026-98039.