# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104324, BELL-CVE-2026-98043, DEBIAN-CVE-2026-98043, GHSA-w7pv-jwfv-f7cm, UBUNTU-CVE-2026-98043

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98043 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-98043 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98043/ (Markdown: https://insights.sbomify.com/CVE-2026-98043/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98043
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98043
- OSV: https://osv.dev/vulnerability/CVE-2026-98043

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98043/
Summaries are generated and may contain mistakes; the official description above is the record.