CVE-2026-98034 bpf: Mark NULL kptr stores precise
A Linux kernel BPF verifier flaw allows attackers to bypass checks and write arbitrary data to kernel pointers, potentially leading to privilege escalation.
- 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-2026-98034?
CVE-2026-98034 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: Mark NULL kptr stores precise
check_map_kptr_access() permits a scalar store into an untrusted kptr field only when the register is known to contain zero. Unlike other verifier checks whose outcome depends on a scalar value, it does not mark that register precise.
A state checkpoint reached with an imprecise zero can therefore prune a second path that reaches the store with an arbitrary nonzero scalar. The program can write attacker-controlled bits into the kptr field and load them back as a PTR_TO_BTF_ID.
Call mark_chain_precision() before accepting a known-zero register. This forces state equivalence to compare its scalar range and makes the verifier visit and reject a path carrying a nonzero value.
Which versions are affected by CVE-2026-98034?
How do I fix CVE-2026-98034?
Apply the vendor's patch.
Is CVE-2026-98034 being exploited?
There is no known exploitation of CVE-2026-98034 in the wild and no public exploit code.
Sources
Also known as AZL-104498, BELL-CVE-2026-98034, DEBIAN-CVE-2026-98034, GHSA-r89f-4x69-4v8p, UBUNTU-CVE-2026-98034.