CVE-2026-98037 bpf: Reject untrusted allocated-object pointers
A local attacker can exploit a use-after-free vulnerability in the Linux kernel BPF subsystem to execute arbitrary code or escalate privileges.
- 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-2026-98037?
CVE-2026-98037 is an use after free 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: Reject untrusted allocated-object pointers
When the final RCU read-side critical section ends, a local kptr is demoted to PTR_UNTRUSTED but retains MEM_ALLOC. The pointer may be NULL or may refer to an object whose lifetime is no longer protected.
type_is_ptr_alloc_obj() nevertheless recognizes any PTR_TO_BTF_ID with MEM_ALLOC as a live allocated object. In particular, a refcount-only local kptr never carries NON_OWN_REF, so it still passes the bpf_refcount_acquire() argument check after RCU protection ends. The kfunc can then dereference NULL or stale memory.
Make type_is_ptr_alloc_obj() reject PTR_UNTRUSTED pointers. Since type_is_non_owning_ref() is based on the same predicate, graph kfunc arguments obey the same live-object requirement. Fault-protected reads of the demoted pointer remain valid: writes are already rejected, and read fixups use bpf_may_fault_on_deref() rather than this predicate.
[ kkd: Rewrote commit log ]
Which versions are affected by CVE-2026-98037?
How do I fix CVE-2026-98037?
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-2026-98037 being exploited?
There is no known exploitation of CVE-2026-98037 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98037, DEBIAN-CVE-2026-98037, GHSA-3hhf-gmj4-q58c, UBUNTU-CVE-2026-98037.