CVE-2026-98043 bpf: Don't infer non-NULL from a pointer with an unbounded offset
A flaw in the Linux kernel BPF verifier allows local attackers to trigger a NULL pointer dereference, causing a system crash.
- 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-2026-98043?
CVE-2026-98043 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: Don't infer non-NULL from a pointer with an unbounded offset
reg_not_null() decides that a register holds a non-NULL value by looking at its type alone. For pointer types that allow arithmetic the type only guarantees a non-NULL base, in case of an unbound offset the runtime offset value might still add up to NULL. Consider the followng program:
r6 = bpf_map_lookup_elem(map, &0); /* present */ if (r6 == 0) return 0; r7 = bpf_map_lookup_elem(map, &1); /* absent, NULL at runtime */ r8 = r7; r8 -= r6; /* pointer - pointer: unknown scalar, -r6 */ r8 <<= 1; r8 >>= 1; /* any non-negative offset is accepted by */ /* check_reg_sane_offset_ptr() */ r6 += r8; /* verifier: map value; runtime: zero */ if (r7 != r6) return 0; *(u8 *)(r7 + 0); /* r7 is inferred non-NULL, both are zero */
At runtime both registers are zero, the comparison is true and the load faults with NULL pointer dereference.
Require the offset to be within +-BPF_MAX_VAR_OFF in reg_not_null().
Which versions are affected by CVE-2026-98043?
How do I fix CVE-2026-98043?
Apply the vendor's patch.
Is CVE-2026-98043 being exploited?
There is no known exploitation of CVE-2026-98043 in the wild and no public exploit code.
Sources
Also known as AZL-104324, BELL-CVE-2026-98043, DEBIAN-CVE-2026-98043, GHSA-w7pv-jwfv-f7cm, UBUNTU-CVE-2026-98043.