# 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.

- **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-104498, BELL-CVE-2026-98034, DEBIAN-CVE-2026-98034, GHSA-r89f-4x69-4v8p, UBUNTU-CVE-2026-98034

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98034 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-98034 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-2026-98034/ (Markdown: https://insights.sbomify.com/CVE-2026-98034/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98034
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98034
- OSV: https://osv.dev/vulnerability/CVE-2026-98034

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98034/
Summaries are generated and may contain mistakes; the official description above is the record.